clean the rims with carb cleaner to remove all the brake dust and crap, then sand them with 180 grit, then 320 grit, then wipe the rims down with laquer thinner then use a good adhesion promoter, and a good quality paint.
i prefer duplicolor myself, id use there adheasion promotor, then either there engine paint, or use rustoleums hammer tone for a cool look. and that paint is tuff stuff.
just make sure to use a high heat paint, those rims can get hot after a long day in traffic.
ive successfully painted a set of chrome rims, but used automotive paint and clear, on a tire machine twice and all, still holding up 4 years later.