I have this "DIY" on my "to-do" list but I haven't got around to it yet. I bought my Crossfire used and 2 of the 4 rims were scuffed. The results in the "DIY" looked pretty good. Assuming the damage is only cosmetic and the rims are painted not polished. I bought german wheel paint/primer from Einszett of North America. (Note: I plan to remove the wheel from the car rather than mask the whole car).

http://www.audiworld.com/tech/ext43.shtml