Kleen Strip in the spray can works fairly well (
http://www.walmart.com/ip/Klean-Strip-P ... r/17208799). It may take several applications. It sometimes helps to break the surface with #400 paper first.
The interior of the hub tends to be a bit more of a rough casting - If you want it smooth sand with #220 wet or dry and follow with #400 wet. If you have a buffer then go to polishing. If you don't have a buffer then sand with progressively finer paper wet.
I have a 2hp buffer and use 8" wheels. I this case I used two 1/8" wheels together and started with a coarse (black) compound and eventually finished with white (polish).
A drill and buffing pad will work but generally it turns too slow. It will take awhile. I prefer to use commercial compounds. They seem better (Try Caswell). Here's a link to their buffing instructions -
http://www.caswellplating.com/buffman.h ... uffman.htm
As you can see from the pic this one is not perfect - Sometimes the aluminum is so bad it is impossible to get it perfect.