I have a set of alloy wheels with faded silver paint and some minnor curb rash that I would like to clean up, and possibly change to annother color, like antracite or bronze. They currently have some very stuck on brake dust too. The center covers are plastic and they don't have tires on them right now.
Any tips for making these things look like new on a challenge budget?
Funny, I was just reading this the other day.
thats a good diy but doesnt address curb rash. I too have a set of wheels, they have a lot of spokes though so I am trying to avoid a full repaint. I just want to "repair" the curb rash cheap and just touch up the paint in those areas.
Can you bondo the curb rash and try to smooth it out before painting?
Yup.
I've cleaned up some pretty nasty rash with filler.
I wouldn't use Bondo, but I've used All-Metal with pretty good success. It takes a long time to do a nice repaint on a set of alloys.
Excellence magazine had a pretty good article on wheel refinishing about a year and a half ago. I'll try to find a link to it.
Issue #172, April 2009
To clean them and get the paint off, use oven cleaner.
Or a blasting box. That's how I cleaned up my Civic wagon's wheels (barely visible on the Miata in my avatar). Them I primed and painted them that dark graphite sort of color. They're steel, but they look like alloys now. 
As with any paint job, it's all in the prep. I still have a set of Saturn alloys that I painted the same color about 5 years ago. They look OK but with inferior prep the paint's come off in a couple of places. Not bad at all, but could be better. My former friend curbing one of them didn't help. 
As far as plastic covers and such go, just paint them at the same time you paint the wheels. The wheel paint will stick, and the covers will match. I seriously considered repainting Miata #2's daisy wheels solely because the center caps had faded to ugly plastic rather than the original silver. The wheels themselves were fine. 
