Paint job help

My son tried rolling some Rustoleum on his car, as seen in the many youtube.com videos. But when it came time to rub it out, manischewitz, was that stuff ever resistant to sanding! It seemed to have quite a rubbery texture which the sandpaper just couldn't bite into. So although in general I like Rustoleum, I would definitely recommend against using it for a roller or brush job that has to be sanded smooth after the paint has dried.