For starters rattle can paint lays down very thin, so you want to do as little sanding as possible. Now to make paint look decent the first thing you need to buy is a 3m maroon pad. Most auto parts stores sell them in a 3 pack. Next softly scuff the surface you are going to paint with the 3m pad, this gives the paint something to hook to. Next spray the color, coats doesn't matter, you want full color coverage, meaning paint it till it all looks the same. Now for the tricky part, if it's a metallic color you need to paint in lite coats. If you go to heavy the metallics can sink in the paint, and it won't look right. If you need you can do a final fog coat where you spray from a larger distance this help lay the metallics right on top. Next let it dry then you can clear over it. If its been drying for a day you should scuff it up again with the 3m before you clear.
Really the only time you sand between coats is when you did a crappy job with the last coat you painted, or it has been like 8 hours since your last coat of paint.
get the scotch brite pads...