With the machines and cleared wheels - SOAP and WATER is the best method for cleaning in order to NOT damage the outer coating; however, if you have any staining or excessive grease that has buried into the pores of the finish - Eagle1 makes a "Mag Wheel" cleaner that will break down anything on the surface; however, use caution.
my suggestions is to wash the wheel with soap and water - wash all of the soap off - apply the Eagle1 product - quickly agitate with a soft brush and remove fully with a LOT of water. If left on the wheel, the cleaner will stain the clear finish forever. This is the most drastic method you can take other acid washing the clear coating off and spending the rest of eternity hand polishing the raw aluminum.
Westley's Bleach White and/or ammonia both work well as a mild treatment if needed.