etl,
I would say if you can get them to a sand/ media blaster then do so. They will be able to remove all of the paint (and any rust) from the rims and give you a nice clean surface to paint. For an even more durable coating you could have them powder coated. It shouldn't be too expensive as I looked into having my wheels two toned and it was going to be $200-$300 per wheel to have the chrome stirpped off of them, prepped and two tone powder coated.
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong, it usually turns out to be impossible to get at or repair."
-Douglas Adams, Mostly Harmless