Hi Pete, try using a piece of threaded rod to chuck your spinner cone in a drill press set to low - medium speed. Starting with 600 grit al/oxide paper you work on removing the fine machining marks in the aluminum. As the finish progressively improves you move to 800, 1000, and so on until you can switch to rubbing compound. The rubbing compound will begin to bring out a mirror finish, once you've got that you finally go with an aluminum polish like Mothers to top it off. One word of caution . . . watch the prop cut outs if you use the drill press method - they'll bite.
How's that Yak comin?

Ty

www.rcaerobatix.homestead.com