It is Very easy to gouge a plastic bumper (cover) with a sanding disk. Is the bumper plated steel? You may be better off using a hand sanding block or try a friends DA electric sander with 120-180 grit. No need to remove all the paint--it's your best primer![]()
Forget the silly drill..Buy a small pack of 320/400 automotive sandpaper. fold it in half 3 x and wet sand with water from a hose.. you will have better results than a drill sanding pad..![]()
2nd this. I wouldn't use a circular sander on it. The paint will come off pretty easily by hand. I'd use the fine grit that they mentioned, too.do not use a spinning, round sanding drum or disk on a drill, in an attempt to sand a plastic bumper. you will not have an acceptable surface after trying it.
if you are broke, hand sanding something that size wont be a big deal.
also, take retrosbuilders advice too, plastic bumpers dont take well to regular paint.