Hi Bob,
Bare aluminum sheet from the rolling mill would have a semi flat surface. About the only way that I can think of is to use very fine wool. You have to be careful using steel wool, that you don’t leave any very fine steel particles in the surface of the alum or you will get small points of corrosion. If you could anodize it after buffing it would give it a nice uniform slightly satiny finish. Anodizing would be relatively easy using a battery, dilute sulfuric electrolyte and an alum foil or sheet anode over the plate. Check the surface for continuity and when you get none you have deposited the oxide that will protect it and soften the finish.
Just an idea.
Denny Graham
Sandwich, IL
