Try this if you want to put a fine finish on your aluminum parts.
1 a piece of thick float glass for your base
2 a handle of some sort, I just use a block of walnut I found on the floor
3 full sheets of 100, 120, 150, 220, 320 and, if you’re going all out, 400 and 500 or even finer if you like
4 a roll of double stick tape
5 a roll of painters tape. (the double stick I use really likes to stick to aluminum so I use painters tape between it and the aluminum)