Anyone tried this successfully? I want to put some better front fenders on my car (passenger side is pushed in, drivers side has a small rust spot) and paint my bumpers (rear is spider cracked, front has paint rubbed off on the corners and is fading). My car is 8E3 Blue, Metallic.. The local auto parts store can mix it for me and I have all the equipment to spray(guns, large compressor etc). How would I go about prepping the plastic bumpers? safe to use a fine grit sandpaper on it so the paint has something to stick to? I have pretty much every thing from 40-600 grit and an orbital sander. Ive never painted a car or anything that needs alot of prepping so this will be a first.