I have buffed a LOT of aluminum and it depends a lot on the condition of the base metal. If it is BLACK then your going to need that coating removed before you try to buff. In the worse case condition you may need to sand blast it to expose fresh metal. Then a wire brush to smooth things up. Then sand paper and some times even a file! Then you can start with a sewn wheel and course compond. As the polish comes in you will need to switch to an open wheel and softer compond.
In a phrase; it takes a lot of elbow grease. Even with power tools (bench grinder or die grinder). It is also a very dirty job! If you did the job right you will need a bath when your done.