James, unless they're pretty beat up I'd just use some good chrome polish and a bit of elbow grease. I'll bet you can get them looking pretty good. As for keeping them looking good I recommend a plastic coated dead blow hammer for the knock offs instead of the leather, brass, or lead ones commonly used. Not expensive and they won't mar the knock off or the wheel if you miss with a blow, and the reduced rebound makes them easy to use. A 3 or 4 pound hammer works great.
As for powder coating the wheels, I agree with Stan, they'll soon crack around the spokes and then you have a problem getting the powder coating blasted off to redo them. Stick with paint for those.