Spray paint should do fine. I've always liked Krylon the best.
Here's a trick I learned when I was in the car business... First scrape off the flaking paint with a wire brush and clean the wheels real good with something like paint thinner or denatured alcohol, tape off the lug nuts and hub, then (here's the trick) take an old deck of playing cards and slip them between the rim and the tire going all the way around. That way you don't have to take the wheel off the trailer or the tire off the rim to get a good looking job.
Hope this helps...
Harpo
