plasti-dip is still the rage. if you don't like the colors they offer, i've read about people plasti-dipping first, then spraypainting whatever color/texture over that so you can still have that durable, removable undercoat with a shell of paint on top. clear coat is probably smart too.
you can leave the wheels on if you want, but you'll get better coverage and probably do a better job of cleaning and taping if you remove them. the cleaner the wheels (or whatever surface you're dipping) are, the better adhesion you'll get. if i weren't so busy this weekend i would practice on my spare wheel. if you do a quick search of the term "plasti" you'll find tons of threads with photos and ideas. i'll probably end up doing all my badges, but i'm torn on whether or not i want to do my grille.