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

[silviaz]

11 minutes ago, GTSBoy said:

More likely from tiny bubbles in the filler/putty. Maybe be less aggressive when mixing it. Perhaps invest in a vacuum chamber to pull the air bubbles out?**

**I don't know if this is a thing for body filler. I see hardcore epoxy makers degassing their mixed resin on the regular.

Ah ok. I seem to be mixing it like everyone else does so not sure what's happening. Will experiment with it more.

[GTSBoy]

Your other option is to buy a spray can of hi-fill and prime it with some pinholes. See if the primer makes them disappear. If it does, then you can leave it with pinholes of that size and they will go away when the painter takes over.

[Murray_Calavera]

@silviaz first thought is you are folding air into the filler as your mixing the hardener through it, GTS beat me to that. 

Next thought is, maybe too much hardener was used. 

Unfortunately there are a lot of variables that can give you pinholes. Maybe consider weighing out the filler/hardener to remove this variable. 

[silviaz]

2 hours ago, Murray_Calavera said:

@silviaz first thought is you are folding air into the filler as your mixing the hardener through it, GTS beat me to that. 

Next thought is, maybe too much hardener was used. 

Unfortunately there are a lot of variables that can give you pinholes. Maybe consider weighing out the filler/hardener to remove this variable. 

I rewatched some video tutorials of other people doing it, and compared it to mine, I think I might be mixing it faster than the other guys. @GTSBoy when you said aggressively I guess this falls under that. The level of hardener seems consistent, I'll experiment with it more and report back.

[silviaz]

On 01/06/2025 at 12:36 PM, MBS206 said:

To expand on this to help understanding...

The bigger/longer the block is, the more it's going to work to sit on your far away high areas, and not touch the low stuff in the middle.

When you throw the guide coat, and give it a quick go with a big block, guide coat will disappear in the high spots. If those high spots are in the correct position where the panel should be, stop sanding, and fill the low spots.

However, using a small block, you "fall off" one of the high spots, and now your sanding the "side of the hill".

Your little block would have been great for the stone chips, where you only use a very small amount of filler, so you're sanding and area let's say the size of a 5/10cent piece, with something that is 75*150.

For the big panel, go bigger!

 

And now I'll go back to my "body work sucks, it takes too much patience, and I don't have it"

PS, I thought your picture with coloured circles was an ultra sound... That's after my brain thought you were trying to make a dick and balls drawing...

I ended up in this rut again lol, and used a shit ton of filler. One thing I can't understand is, even after using a big long block and going in long X pattern strokes, I always end up at bare metal again with no filler, and my repair started at one end of the door and now I've chased my tail to almost the other end of the door. I was thinking of hitting the panel with a hammer where it might be a high spot and making everything low then filling it, I did this on a small section on my other door by mistake and I think I fixed it lol. Is this a bad idea?

The other thing is with guidecoat, whether it's the powder or spray, after I sand all the guide coat off, it doesn't reveal anything for me in terms of high spots and low spots and makes it especially hard when it's bare metal (at least in powdered form), am I doing something wrong here, or likely a high spot I keep going over and creating valleys?

Lastly, stupid question but, is it possible that after sanding if I only sand over the filler area where I know to be a dent that it's impossible for me to dig into that dent? Unless there are other problems which I missed.

 

Edited Saturday at 09:50 AM by silviaz

[Murray_Calavera]

@silviaz

Are you skim coating the entire panel (covering the entire panel with filler) before your hitting it with the long block? Or are you selectively applying filler to the repair, trying to fill the low points? 

On 13/09/2025 at 7:43 PM, silviaz said:

I was thinking of hitting the panel with a hammer where it might be a high spot and making everything low then filling it,

Please don't do that. 

On 13/09/2025 at 7:43 PM, silviaz said:

Is this a bad idea?

Almost certainly.

On 13/09/2025 at 7:43 PM, silviaz said:

The other thing is with guidecoat, whether it's the powder or spray, after I sand all the guide coat off, it doesn't reveal anything for me in terms of high spots and low spots and makes it especially hard when it's bare metal (at least in powdered form), am I doing something wrong here, or likely a high spot I keep going over and creating valleys?

Are you checking the panel for flatness as you go? Or is it more a case of, sand til all the guide coat is gone then check? 

[silviaz]

23 hours ago, Murray_Calavera said:

@silviaz

Are you skim coating the entire panel (covering the entire panel with filler) before your hitting it with the long block? Or are you selectively applying filler to the repair, trying to fill the low points? 

Please don't do that. 

Almost certainly.

Are you checking the panel for flatness as you go? Or is it more a case of, sand til all the guide coat is gone then check? 

So I'll put filler past the repair area a bit to make sure I don't miss anything. Then I'll block it until it's almost level, put the guidecoat, then keep blocking until it's gone. Then it's still wavy. 

In regards to hitting the panel, I saw this video might give more context -

Skip to 0:47 he knocks it down.

But yeah I'm sanding until the guidecoat is gone then checking because otherwise my filler is still well above the bodyline. Unless what you're saying is I should put guidecoat around it early, surrounding the filler then stip once it's gone?

[Murray_Calavera]

29 minutes ago, silviaz said:

In regards to hitting the panel, I saw this video might give more context -

Yeah makes sense, hard to comment on your situation without seeing what your doing. I was talking generally before, I would not be looking to randomly create low spots with a hammer to then have to fill them. 

44 minutes ago, silviaz said:

So I'll put filler past the repair area a bit to make sure I don't miss anything. Then I'll block it until it's almost level, put the guidecoat, then keep blocking until it's gone. Then it's still wavy. 

43 minutes ago, silviaz said:

But yeah I'm sanding until the guidecoat is gone then checking because otherwise my filler is still well above the bodyline. Unless what you're saying is I should put guidecoat around it early, surrounding the filler then stip once it's gone?

It's hard without seeing what your doing, it sounds like you are using the guide coat to identify low spots, as you're saying the panel is still wavy. I don't see how you're not ending up with patches of guide coat remaining in a wavy panel? Once the high spots are knocked down to the correct level, surely to have a wavy panel you need low spots. And those low spots would have guide coat still in them?

[silviaz]

6 minutes ago, Murray_Calavera said:

Yeah makes sense, hard to comment on your situation without seeing what your doing. I was talking generally before, I would not be looking to randomly create low spots with a hammer to then have to fill them. 

It's hard without seeing what your doing, it sounds like you are using the guide coat to identify low spots, as you're saying the panel is still wavy. I don't see how you're not ending up with patches of guide coat remaining in a wavy panel? Once the high spots are knocked down to the correct level, surely to have a wavy panel you need low spots. And those low spots would have guide coat still in them?

I haven't knocked them down yet. I think I made the repair more complex than it should have been. I had rock chips combined with waviness and dents and I tackled it all in one because it was near each other and just end up wasting a bunch of bog lol.

I'll knock down those areas and see how I go.

And yep what you are saying at the end is correct. I think I might be sanding the top of a steep hill then my sanding block falls into the dent and gets rid of the guidecoat if that makes sense. Though shouldnt unless I'm covering too big of an area with not a long enough block.

I'll try something new and provide some updates. Getting there though! Thanks as always.

 

[Murray_Calavera]

6 minutes ago, silviaz said:

waviness and dents

Did you panel beat the dents or have you tried to repair this only using filler? 

6 minutes ago, silviaz said:

I think I might be sanding the top of a steep hill then my sanding block falls into the dent and gets rid of the guidecoat if that makes sense.

Is your sanding block soft/flexible and is following the shape of the panel rather then just knocking down the high points? 

[MBS206]

I think Murray is onto it.

It's sounding like either it's a soft block, not long enough block, OR if you're chasing waves, you're going in the direction of the waves, instead of across them.

Rotate your sanding pattern by 45 degrees is something to try. You said you're going in an X, so now instead, from the same perspective, do a "t" instead.

 

If you're not able to have the block sit on top of two high points, and not touch the low point between them, you'll never get it flat.

[silviaz]

2 hours ago, Murray_Calavera said:

Did you panel beat the dents or have you tried to repair this only using filler? 

Is your sanding block soft/flexible and is following the shape of the panel rather then just knocking down the high points? 

Tried to repair with filler only. The block is a foam block but quite hard and I put a velcro on it for sandpaper, the hook and loop system. It's not one of those super soft ones that just follow the panel. Similar to a dura block.

Edited 2 hours ago by silviaz

[silviaz]

52 minutes ago, MBS206 said:

I think Murray is onto it.

It's sounding like either it's a soft block, not long enough block, OR if you're chasing waves, you're going in the direction of the waves, instead of across them.

Rotate your sanding pattern by 45 degrees is something to try. You said you're going in an X, so now instead, from the same perspective, do a "t" instead.

 

If you're not able to have the block sit on top of two high points, and not touch the low point between them, you'll never get it flat.

I see what you mean on that last paragraph and makes sense. I am leaning towards because I made the repair/filler area large that I didn't use a long enough block. Will minimise the area and let you's know how I go.

This is random but I noticed when I put epoxy primer it felt flat but that's just temporary.