hi mate,
some paints require a Ground Coat which is usually the metallic colours. just double check if you need this or not.
I wouldn't fill the minor scratches with bog.. just use primer filler or a spray putty.
just to make it clear. will you be using acrylic paint or twopac? I would not recommend using two pac paint in a garage as you need a proper booth. with acrylic you can get away spraying your car in your garage and depending on the coverage I would personally put on 3-5 coats and 3-4 coats of clear on top.
Also, with acrylic paint, you need to wait for to paint to cure for couple of days, wet sand and and cut and polish after.