I started with some sandpaper I had maybe 100 grit. Way too abrasive. Finished with 220 grit. They even make a 320 or maybe even some wetsanding paper. I finished with a hard grade buffing wheel on my angle grinder with some buffing compound which was green for high gloss materials.
In between buffings I treated the aluminum with oven cleaner.
It's real easy once you find your method.