I've used that aluminum cleaner that was in the link above. IIRC, harbor freight had it, purple label, said "aluminum brightener" on it.
I had stripped an entire 1542 Grumman flat bottom, then cleaned it with the aluminum brightener. I ALMOST left it, it looked like literally a brand new boat. But I wanted it camo from day one when I bought it (well...day two actually). So I started in with some home-made patterns and 5 colors of camo paint and it came out wonderful. Dec 31st will be 6 years since I painted it. And it still looks exactly the same as it did then, except for a few scratches where the timber got against it, but it didn't scratch THROUGH the paint, just the surface.
i've also used that aluminum brightener, cut 1:1 with water, for cleaning engines, transmissions, anything aluminum. BUT you have to be careful with it becuase if you leave it on long, it'll turn it black. Works well on dirt-stained bare aluminum engine, transmission, and differential cases