In my opinion, sandblasting is the best method. It gives a slightly rough finish so the coating - primer or powdercoating gets some bite to adhere better. Here in the Twin Cities, there are several places that will blast a wheel for $20 to $35. These a large sandblasting outfits that can do a rim in a very short time. Personally I blasting my own rims so I can prime them quickly after blasting, however it takes about an hour to do each one. Once sandblasted, you can see any defect in the metal like cracks in the hub or dings. What you can't see for sure is whether a lug nut hole is enlarged or the rim is bent - wobble). I have done 12 or 15 so far with my TIP (100# for sand) pressure blaster and am happy with the results.
Rusty Nelson