Steps to DIY sanding car back ready for respray....

[Murray_Calavera]

On 20/05/2025 at 9:57 PM, silviaz said:

If I do a spot repair and I put filler in a dent for example and sand outside of the repair with 320 grit lets say so the primer can stick as I will only put primer on that repair and the surrounding area and then repaint the whole panel.

Sounds good. 

On 20/05/2025 at 9:57 PM, silviaz said:

Don't I need to make sure that I don't put primer on the old clear coat? I keep seeing YouTube videos where people have new paint and primer land on the old clearcoat that isn't even dulled down, it's still shiny. I thought putting paint on clearcoat or primer on clearcoat is a bad idea because it won't stick.

I don't 100% understand what your getting at here. When you say, "I keep seeing YouTube videos where people have new paint and primer land on the old clearcoat that isn't even dulled down" do you mean this - there is a panel with factory paint, without any prep work, they paint the entire panel with primer, then colour then clear? 

If that's what you mean, sure it will "stick" for a year, 2 years, maybe 3 years? Who knows. But at some stage it will flake off and when it does it's going to come off in huge chunks and look horrific. 

On 20/05/2025 at 9:57 PM, silviaz said:

Don't I need to make sure that I don't put primer on the old clear coat?

Of course read your technical data sheet for your paint, but generally speaking, you can apply primer to a scuffed/prepped clear coat. Generally speaking, I wouldn't do this. I would scuff/prep the clear and then lay colour then clear. Adding the primer to these steps just adds cost and time.

On 20/05/2025 at 9:57 PM, silviaz said:

I thought putting paint on clearcoat or primer on clearcoat is a bad idea because it won't stick.

It will stick to the clear coat provided it has been appropriately scuffed/prepped first. 

On 20/05/2025 at 9:57 PM, silviaz said:

So in this scenario it's a bit different to mine but imagine someone doing a spot repair and only painting that small section of repair but the new paint is landing on the old clearcoat.

When you say, "but the new paint is landing on the old clearcoat" I am imagining someone not masking up the car and just letting overspray go wherever it wants. Surely this isn't what you mean? 

So I'll assume the following scenario - there is a small scratch. The person manages to somehow fill the scratch and now has a perfectly flat surface. They then spray colour and clear over this small masked off section of the car. Is this what you mean? If this is the case, yes the new paint will eventually flake off in X number of years time. 

The easy solution is to scuff/prep all of the paint that hasn't been masked off in the repair area then lay the paint. 

1 hour ago, silviaz said:

Bit of a similar question, apprently with epoxy primer you can just sand the panel to 240 grit then apply it and put body filler on top.

So you want to prep the surface, lay primer, then lay filler, then lay primer, then colour, then clear? 

Life seems so much simpler if you prep, fill, primer, colour then clear. 

1 hour ago, silviaz said:

So does that basically mean you almost never have to go to bare metal for simple dents?

There are very few reasons to go to bare metal. Chasing rust is a good example of why you'd go to bare metal. 

A simple dent, there is no way in hell I'm going to bare metal for that repair. I've got enough on my plate without creating extra work for myself lol. 

[silviaz]

16 hours ago, Murray_Calavera said:

Sounds good. 

I don't 100% understand what your getting at here. When you say, "I keep seeing YouTube videos where people have new paint and primer land on the old clearcoat that isn't even dulled down" do you mean this - there is a panel with factory paint, without any prep work, they paint the entire panel with primer, then colour then clear? 

If that's what you mean, sure it will "stick" for a year, 2 years, maybe 3 years? Who knows. But at some stage it will flake off and when it does it's going to come off in huge chunks and look horrific. 

Of course read your technical data sheet for your paint, but generally speaking, you can apply primer to a scuffed/prepped clear coat. Generally speaking, I wouldn't do this. I would scuff/prep the clear and then lay colour then clear. Adding the primer to these steps just adds cost and time.

It will stick to the clear coat provided it has been appropriately scuffed/prepped first. 

When you say, "but the new paint is landing on the old clearcoat" I am imagining someone not masking up the car and just letting overspray go wherever it wants. Surely this isn't what you mean? 

So I'll assume the following scenario - there is a small scratch. The person manages to somehow fill the scratch and now has a perfectly flat surface. They then spray colour and clear over this small masked off section of the car. Is this what you mean? If this is the case, yes the new paint will eventually flake off in X number of years time. 

The easy solution is to scuff/prep all of the paint that hasn't been masked off in the repair area then lay the paint. 

So you want to prep the surface, lay primer, then lay filler, then lay primer, then colour, then clear? 

Life seems so much simpler if you prep, fill, primer, colour then clear. 

There are very few reasons to go to bare metal. Chasing rust is a good example of why you'd go to bare metal. 

A simple dent, there is no way in hell I'm going to bare metal for that repair. I've got enough on my plate without creating extra work for myself lol. 

Thanks for all that information I appreciate it. To answer your questions:

- Yep that's what I mean. These guys are professional painters to so I must be missing something. It's a bit hard to explain.

- With the primer landing on clearcoat, I make sure that the surrounding clearcoat is scuffed to 240 grit as my epoxy primer says that I only need to sand the area to 240 grit.

- Yeah so similar to the first question, assuming that the paint landed on the unscuffed clearcoat because I've seen that happen.

- Yep I want to prep the surface in that order. Only reason because epoxy primer will protect it from rust and I need that atm with this crappy Sydney weather. I think I was worried about time, if I try to put the filler down but screw it up somehow and I don't have time to sand it off and reapply it then need to put primer later that it might start to rust again so I wanted to apply the primer as quick as possible to not deal with rust. 

- I just deleted some answers, I just realised after watching a video and what you said about looking at the data sheet, that I need to read the data sheet on the specific filler I'm using. It's possible now that I put epoxy primer first was a waste of time and need to go to bare metal lol

Edited May 23 by silviaz

[Murray_Calavera]

1 hour ago, silviaz said:

- Yep that's what I mean. These guys are professional painters to so I must be missing something. It's a bit hard to explain.

Post up the youtube video your referring to, will be much easier then us playing charades together lol. 

1 hour ago, silviaz said:

- Yeah so similar to the first question, assuming that the paint landed on the unscuffed clearcoat because I've seen that happen.

Lets see the videos in question. 

1 hour ago, silviaz said:

Only reason because epoxy primer will protect it from rust and I need that atm with this crappy Sydney weather

If the car is in your garage and you sand it back to bare metal, you'd be surprised how much time you have to work with before it starts to rust. As long as you're actively working on the car in your free time, you're going to be fine. 

1 hour ago, silviaz said:

I need to read the data sheet on the specific filler I'm using

I assume everyone is reading the data sheets for all the materials they are using before using them. If you're not, please start doing this lol. 

[silviaz]

2 minutes ago, Murray_Calavera said:

Post up the youtube video your referring to, will be much easier then us playing charades together lol. 

Lets see the videos in question. 

If the car is in your garage and you sand it back to bare metal, you'd be surprised how much time you have to work with before it starts to rust. As long as you're actively working on the car in your free time, you're going to be fine. 

I assume everyone is reading the data sheets for all the materials they are using before using them. If you're not, please start doing this lol. 

Yep I'll find those and get back to you. To be honest I wasn't aware of data sheets until you mentioned it. I'm still new to this haha, lots to learn. My car is parked outside, it rusted in less than 24 hours lol. Only minor surface rust that was easily removed but I've been worried that it might rust from the inside out and screw me over in the long term (if I decide to keep the shitbox for that long).

[silviaz]

24 minutes ago, Murray_Calavera said:

Post up the youtube video your referring to, will be much easier then us playing charades together lol. 

Lets see the videos in question. 

If the car is in your garage and you sand it back to bare metal, you'd be surprised how much time you have to work with before it starts to rust. As long as you're actively working on the car in your free time, you're going to be fine. 

I assume everyone is reading the data sheets for all the materials they are using before using them. If you're not, please start doing this lol. 

Ok I FINALLY found a video lol. This took way longer than it should have as I could have sworn I saw multiple videos like this. I kept finding the completely opposite (the correct way of doing this). I wouldn't be surprised if I f**ked this up somehow. 

I just realised where I've been getting confused and even with other things I work on. I haven't been doing things the regular way instead I'm going a roundabout way of doing things, like putting epoxy primer first then filler for example instead of putting just filler then primer on top of that, then wondering what happens if I get that primer on the clear coat that I haven't sanded yet. This was a bit of an epiphany 😂 

But anyways, here this video. Time stamp, 2:56, some of the primer lands on the paint unscuffed above. You can see from the reflection it looks shiny.

 

[Murray_Calavera]

@silviaz

Ok cool, so much easier with a video. I can see why this video would be confusing for new players.  

It is obvious that this entire bonnet is going to be resprayed, have a look in the background around 2:05, you can see a bunch of bare metal on the left side of the bonnet. 

It's not an issue for the primer being laid down on the non-prepped clear on the bonnet. It will be sanded off at a later stage. 

This might not be obvious to new players, but working on bare metal and factory paint in this instance, the factory paint is like a mountain and the bare metal is a huge valley. The bonnet needs to be levelled flat before it receives it's final stage of colour and clear coat. During this levelling process, the primer that is landing on the clear that you are worried about will be removed. 

Also, this guy is out of control. Zero PPE while spraying, maybe he is a good example overall about what not to do lol.

[silviaz]

3 hours ago, Murray_Calavera said:

@silviaz

Ok cool, so much easier with a video. I can see why this video would be confusing for new players.  

It is obvious that this entire bonnet is going to be resprayed, have a look in the background around 2:05, you can see a bunch of bare metal on the left side of the bonnet. 

It's not an issue for the primer being laid down on the non-prepped clear on the bonnet. It will be sanded off at a later stage. 

This might not be obvious to new players, but working on bare metal and factory paint in this instance, the factory paint is like a mountain and the bare metal is a huge valley. The bonnet needs to be levelled flat before it receives it's final stage of colour and clear coat. During this levelling process, the primer that is landing on the clear that you are worried about will be removed. 

Also, this guy is out of control. Zero PPE while spraying, maybe he is a good example overall about what not to do lol.

Ah ok makes sense, thanks for that clarification it helps a lot. My PPE was terrible recently, I sprayed a can of primer on a panel and the wind blew and I didn't have safety goggles and the mist went in my eye. Didn't take the wind into account, good lesson learned though lol.

 

I guess if I want to be extra careful I can always scuff the whole panel before putting primer like the other videos are doing.

Edited May 23 by silviaz

[silviaz]

3 hours ago, Murray_Calavera said:

@silviaz

Ok cool, so much easier with a video. I can see why this video would be confusing for new players.  

It is obvious that this entire bonnet is going to be resprayed, have a look in the background around 2:05, you can see a bunch of bare metal on the left side of the bonnet. 

It's not an issue for the primer being laid down on the non-prepped clear on the bonnet. It will be sanded off at a later stage. 

This might not be obvious to new players, but working on bare metal and factory paint in this instance, the factory paint is like a mountain and the bare metal is a huge valley. The bonnet needs to be levelled flat before it receives it's final stage of colour and clear coat. During this levelling process, the primer that is landing on the clear that you are worried about will be removed. 

Also, this guy is out of control. Zero PPE while spraying, maybe he is a good example overall about what not to do lol.

A question. So I've attached some images, the red circled ones are where I put 2-3 coats of epoxy primer to protect it from rust. For the purpose of this example let's pretend I won't put body filler there because it's straight and will put 2k primer 3 coats after it's all done. And the last image the paint looks terrible because my paint/clearcoat was all blistered but the scratches are completely smooth and sanded down (I also plan to prime this entire panel) 

My question is

- If I put 2k primer over all those repairs that you see from all 3 images, do I need to sand it because it might show in the paint or should it be fine as it's all smooth and sanded down? 

Edited May 23 by silviaz

[Murray_Calavera]

1 minute ago, silviaz said:

Ah ok makes sense, thanks for that clarification it helps a lot. My PPE was terrible recently, I sprayed a can of primer on a panel and the wind blew and I didn't have safety goggles and the mist went in my eye. Didn't take the wind into account, good lesson learned though lol.

After reading this I think this is really important to mention - please for the love of god do not spray any 2 pack paint (typically advertised as 2K, it contains a hardener that is mixed before spraying) without a proper respirator, gloves, eye protection and preferably a full one piece disposable paint suit. That stuff is nasty and can really f*ck you up. 

Also worth mentioning, the filters on the respirator will require changing before you can smell the chemicals through them. 

So with a brand new respirator and filters, you shouldn't smell anything at all when spraying. If you later can smell the paint chemicals, you've changed your filters too late. 

Filters are cheap, replace them often.

[Murray_Calavera]

Just now, silviaz said:

So I've attached some images

They didn't work.

[silviaz]

Just now, Murray_Calavera said:

They didn't work.

Sorry I reuploaded now.

[silviaz]

1 minute ago, Murray_Calavera said:

After reading this I think this is really important to mention - please for the love of god do not spray any 2 pack paint (typically advertised as 2K, it contains a hardener that is mixed before spraying) without a proper respirator, gloves, eye protection and preferably a full one piece disposable paint suit. That stuff is nasty and can really f*ck you up. 

Also worth mentioning, the filters on the respirator will require changing before you can smell the chemicals through them. 

So with a brand new respirator and filters, you shouldn't smell anything at all when spraying. If you later can smell the paint chemicals, you've changed your filters too late. 

Filters are cheap, replace them often.

Yeah definitely won't. I just thought because this was a quick job, I didn't need more gear even my mask wasn't a proper one but going forward I will use the proper gear. Cheers for that additional info.

Edited May 23 by silviaz

[Murray_Calavera]

43 minutes ago, silviaz said:

- If I put 2k primer over all those repairs that you see from all 3 images, do I need to sand it because it might show in the paint or should it be fine as it's all smooth and sanded down? 

Prior to laying down the primer, you need to make sure the surface is completely level. For example, based on this picture, I strongly suspect that the areas marked in blue are higher then the area marked in green. 

If you spray primer over this entire area, then paint and clear it, the finished result will 100% show the low area. It will stick out like dogs balls. Unfortunately the paint won't magically level out the low areas as you lay it down. 

Without seeing it in person, I expect that the green area will need to be filled, then use a guide coat and check that the entire repair area is level with a large sanding block. 

With this picture, are you saying that even though you can see the scratches, the panel is in fact completely smooth and flat? If this is the case sure you could prep and paint it as it is.  

 

The picture with the paint you described as blistering, it's hard for me to comment on from the photo alone. It looks like the panel is wet? Dunno, looks strange. Does the panel feel as smooth as glass when you run your hand over it?

****

Going back to your question again, generally you would only sand the primer if you made a mistake while laying down the primer. 

If the panel is prepped properly and you lay the primer down properly, you should not need to sand the primer. 

This wouldn't work - Don't prep the panel. Spray primer and see how it turns out. Sand the areas where the issues appear. Spray more primer and see how it turns out. Sand the areas....... Yeah you'd go round and round in circles getting no where. 

[silviaz]

5 minutes ago, Murray_Calavera said:

Prior to laying down the primer, you need to make sure the surface is completely level. For example, based on this picture, I strongly suspect that the areas marked in blue are higher then the area marked in green. 

If you spray primer over this entire area, then paint and clear it, the finished result will 100% show the low area. It will stick out like dogs balls. Unfortunately the paint won't magically level out the low areas as you lay it down. 

Without seeing it in person, I expect that the green area will need to be filled, then use a guide coat and check that the entire repair area is level with a large sanding block. 

With this picture, are you saying that even though you can see the scratches, the panel is in fact completely smooth and flat? If this is the case sure you could prep and paint it as it is.  

 

The picture with the paint you described as blistering, it's hard for me to comment on from the photo alone. It looks like the panel is wet? Dunno, looks strange. Does the panel feel as smooth as glass when you run your hand over it?

****

Going back to your question again, generally you would only sand the primer if you made a mistake while laying down the primer. 

If the panel is prepped properly and you lay the primer down properly, you should not need to sand the primer. 

This wouldn't work - Don't prep the panel. Spray primer and see how it turns out. Sand the areas where the issues appear. Spray more primer and see how it turns out. Sand the areas....... Yeah you'd go round and round in circles getting no where. 

Yep I will use a guide coat after putting filler, I will do it on the whole panel as I'm a beginner so chances I've made quite a few errors. In that photo, I think that was a low spot, I just for example said to pretend it's flat but I will put filler + guide coat after to assess where I'm at.

Yep with that picture, the panel is wet as it rained when I took the photo. But all those scratches are completely smooth, I went over it with 240 grit and can't feel it, even with my nail digging into it.

I was legit thinking to buy a 2k can and spray primer to see how it turns out but then thought to myself it's going to be a mess doing it haha. Good mention there.

Thanks for all that info I think I know what to do next.

[Murray_Calavera]

5 minutes ago, silviaz said:

But all those scratches are completely smooth, I went over it with 240 grit and can't feel it, even with my nail digging into it.

Sounds good. Provided the panel is flat/level I'd be happy to start the painting process. 

6 minutes ago, silviaz said:

I was legit thinking to buy a 2k can and spray primer to see how it turns out but then thought to myself it's going to be a mess doing it haha. Good mention there.

While you are learning, for sure you could do this. Its only paint, you can always sand it all back and start again. Its only your time and money on materials, but while you're learning, really its time and money spent on your education. 

Once you know how to do this bodywork and painting, you won't want to waste your time and money on frivolous activities lol. 

[silviaz]

53 minutes ago, Murray_Calavera said:

Sounds good. Provided the panel is flat/level I'd be happy to start the painting process. 

While you are learning, for sure you could do this. Its only paint, you can always sand it all back and start again. Its only your time and money on materials, but while you're learning, really its time and money spent on your education. 

Once you know how to do this bodywork and painting, you won't want to waste your time and money on frivolous activities lol. 

Yep will do, thanks for all the help.

[silviaz]

3 hours ago, Murray_Calavera said:

Sounds good. Provided the panel is flat/level I'd be happy to start the painting process. 

While you are learning, for sure you could do this. Its only paint, you can always sand it all back and start again. Its only your time and money on materials, but while you're learning, really its time and money spent on your education. 

Once you know how to do this bodywork and painting, you won't want to waste your time and money on frivolous activities lol. 

Luckily I didn't put in etch primer as I just found out it's not compatible with my body filler lol. Also just need to sand the panel anywhere between 150-400 grit so I'm in the clear there. It does say to not apply to soft old paint, I assume that means paint that is flaking, peeling,etc

[Murray_Calavera]

10 hours ago, silviaz said:

It does say to not apply to soft old paint, I assume that means paint that is flaking, peeling,etc

Yes correct. Also, I'd avoid applying it to soft paint (however I doubt you'll ever have to deal with it in practice). So any paint that hasn't fully hardened, could be a 1k paint that never fully hardened or it could be a 2k paint that was laid down thick and hasn't yet fully hardened. 

[silviaz]

8 hours ago, Murray_Calavera said:

Yes correct. Also, I'd avoid applying it to soft paint (however I doubt you'll ever have to deal with it in practice). So any paint that hasn't fully hardened, could be a 1k paint that never fully hardened or it could be a 2k paint that was laid down thick and hasn't yet fully hardened. 

Above you mentioned you only need to sand primer if there's an issue with it but with fillers it says the surface needs to be sanded to X grit beforehand. Does that sorta contradict that point as the primer hasn't been sanded yet? At the same time if I sand the primer, there's a good chance I'll expose the bare metal and I'm just chasing my tail at that point. Or I'll just use a sand sponge instead of sandpaper, it seems to be far finer in terms of abrasiveness as opposed to sandpaper.

From what I understand, filler is like primer and needs scratches from the sandpaper to help it adhere to the panel.

I realised the way I'm doing things is actually a bit counter productive as there's a chance after I put filler I will need to put epoxy primer again as opposed to putting the filler first and potentially no primer if I don't go to bare metal. Will keep this in my mind for the rest of my repairs.

Edited May 24 by silviaz

[Murray_Calavera]

5 hours ago, silviaz said:

Above you mentioned you only need to sand primer if there's an issue with it but with fillers it says the surface needs to be sanded to X grit beforehand. Does that sorta contradict that point as the primer hasn't been sanded yet? At the same time if I sand the primer, there's a good chance I'll expose the bare metal and I'm just chasing my tail at that point. Or I'll just use a sand sponge instead of sandpaper, it seems to be far finer in terms of abrasiveness as opposed to sandpaper.

Yep, if you are applying filler it sounds like there is something wrong with the body lol. Safe to assume there is going to be a lot of sanding going on if your still applying fillers. 

Picture a perfect bare metal panel, smooth as glass. You lay down your primer, it's perfect. (why are you going to sand it?) You lay down the colour and clear, it's perfect. No sanding at all took place and you've got a perfectly finished panel. 

5 hours ago, silviaz said:

At the same time if I sand the primer, there's a good chance I'll expose the bare metal and I'm just chasing my tail at that point.

You won't be chasing your tail, sounds like you were prepping to start laying filler. If your happy with the body after the sanding, there is some bare metal exposed and some areas with primer, no issues at all, start laying the filler. You are safe to lay filler on bare metal or primer (of course check your technical data sheet as usual for what your filler is happy to adhere to). 

5 hours ago, silviaz said:

From what I understand, filler is like primer and needs scratches from the sandpaper to help it adhere to the panel.

This isn't a 100% correct statement. There is primer that is happy to adhere to smooth bare metal. There are fillers that are happy to adhere to smooth bare metal. Just make sure you're using the right materials for the job. 

5 hours ago, silviaz said:

I realised the way I'm doing things is actually a bit counter productive as there's a chance after I put filler I will need to put epoxy primer again as opposed to putting the filler first and potentially no primer if I don't go to bare metal.

Typically if you are using filler, you would go primer, colour and clear. I've never seen any instances before where someone has laid colour over body filler (maybe this happens, but I haven't seen it before). So your plan sounds pretty normal to me.