I do not have a method that does not involve ALOT of hard work, but here goes.
I first scuff the surface with #2 steel wool. This removes most of the surface debris, heavy oxidation, etc. I have tried motorized wire brushes and wheels but this Really scratches too much. Then follow that up with green Scotch brite pads, which removes the scratches the steel wool left. Once again, by hand. Somewhere someone probably has scotch brite pads for a buffer.
Then, I use a variable speed buffer, with Dupont Heavy duty buffing compound.
This is made for paint but it works really well on aluminum.
By the way...did I mention to do this outside, with old clothes or Tyvek suit and old shoes, gloves, far away from anything that you do not want compound on???
I then use Nuvite metal polish, grade C as a finish. You can move on to Grade A and then S if you want, which are finer, which transforms the metal into a mirror.
Maybe not the best system but it works for me. You WILL BE BLACK from the polish residue from head to foot. Or maybe I am just sloppy!
If you are married, remove all clothes and shoes before entering the house, or you won't be married for long!
Several people have suggested Gord's metal polish but I have not tried it.