The statement above about the California Custom aluminum deoxidizer is a good one. That stuff works real well. However it has limitations just like many other things. If all fails get a die grinder (electric or air driven) and put a tapered spindle in it and use some small "Razor Buffs" and a set of polishing bricks. I use a black rouge to cut the nasty stuff first, then a green rouge to polish and white rouge to give the metal a final color. A lot of that stuff can be found at the Eastwood website or even go to your local truckstop---they usually sell it to the drivers for their trucks. Sears or harbor freight has small bricks, also.
Razor buffs are a little harder to find but they are out there. Try this outlet for what I am toalking about.
http://www.woodworkingshop.com/cgi-b...adItem=FO33906
Get the 4" or smaller ones so that the die grinder works them easy and it lets you get into tight places. Do the owrk with a different buff for each type of rouge. Put very little pressure on the buff as you use it. Try it on your fingernail first---that is as hard as you need to apply it ot the wheel. You can clean four wheels in an afternoon.