My secret process for polishing aluminum is a Tumbler, yes like a rock tumbler.
Except I use small industrial type.
I found this on TV a program on how they make coins.
They were using a large vibrator type unit with small stainless steel balls.
Anyway these coin blanks came out beautiful.
I did a test with "BB's" and it came out pretty good, except the BB's went bad after a couple of times.
From there I tried all sorts of stuff, most of it bad, just enough good results to keep me going.
The main trick is the right kind of Soap & water.
Stainless steel Balls cost about $750. for 50 LB. So I tried with what I have. 1/4 inch stainless steel nuts.
I have been using the same nuts for about 2 years now, just starting to round off the points a little bit.

But not only does to do a nice job on the aluminum parts, but the nuts are real, real shinny.
Anyway it has worked out so well I bought 4 of the drums used for tumblers and I made my own rollers I guess you could call them. Two 1/2" rods 4 ft. long supported by 10 ball bearing pillow blocks.
Rubber hose over the rods held in place by hose clamps. Belt driven from a standard 1/4 hp motor.
Runs all four tumblers at the same time.

I put 6 of the angle brackets in each tumbler - Secret is the soap
2 cups of water go into each tumbler with 3 squirts of soap. just enough to cover the bottom of the cup.

The Rim Clean works good for everything except aluminum, copper, stainless steel

The Blue Coral - Wash & Wax works best on aluminum.
When I dump out the tumblers the water is just black, still lots of white suds.
Run time for aluminum is 1-2 hr.

Seems like a long time, but it also de burs all the edges. Actually saves time & labor.