Concur with the sandpaper. A couple sheets of wet or dry, I'd start around a 220 grit, have a sheet of coarser stuff on hand if that does not get the deeper stuff out as fast as you'd like. Start with finer than you may need, it's really easy to go coarse after you see what the part looks like under the finish, and it's a bunch of work to get the scratches of the coarser paper out of the part when you step up.
Get a couple sanding blocks to use for back-up on the paper else you create a random free-form blob of aluminum. I liked blocks of plexiglass, when I had them, but you will want some rigid backers and a softer one or two, along the lines of the hard rubber sanding blocks that are used for doing body work. What you want is some that will stay straight to keep the lines, but you also will need the softer one to stick to the curves without being so soft as to start to get all random and wallowing out weird curves.
Use a bit of warm water with a drop of dish soap in it to keep the paper from plugging up. Work on an old newspaper or an old towel, to keep the mess contained.
Suggest buying a sheet of 180, 2 of each 220, 320, one of 400. Doubt very much you will want to go much higher than 320, if you are refinishing. 600 will get you very close to polished, and unless you want the thing to look like chrome, it's work you don't need to put in to it. If it is getting painted, whether rattle can or baked on, I would take a good look at how it looks at the coarser grit, as you can use a little 'tooth' in the finish for the paint to hold to, and too fine a finish is just work you will bury under the finish.
I have a LOT of experience hand polishing stainless, brass and aluminum up to a mirror finish.
To really get the parts to come out looking really good, you need to watch that you don't blur over the corners, that the straight lines stay so, and the curves stay where they belong. It's pretty low tech work, but there is a great deal more skill in doing a really nice looking job, than it looks like from the outset. Lots of it is in watching cause and effect as you go. Not rocket science, as much as attention to detail and quitting when done, rather than trying to attain perfection. You WILL see every flaw! It comes from staring at it up close for the time you are working on it. Try not to get trapped, eh!
Post some pictures. I'd be interested to see how it goes and what you use for a finish.
Cheers
Trev
