metal polishing
My bike was a rolling basket case that was park outside near the beach for a long time and all the aluminum was deeply pitted and heavily oxidized. With a really bad finish like I had, no amount of hand polishing was going to make the cases look good. As part of the restoration process, I pulled the cases off and had them professionally polished. Smaller parts I polished myself with a kit I got from the Eastwood Company (
www.eastwoodcompany.com). It is an excellent kit and if you have a bench grinder, you can get professional results if you are willing to spend the time. If I recall correctly, aluminum requires a 3 step process with 3 different types of polishing wheels and compounds.
My choice on the finish of my cases was more of a mirror finish than the typical aluminum patina that the bikes came with. For a reference, you can see my bike on the last page of the Visuals section in this site. You can get either type of finish, depending on how much time you spend using each compound. A little experimentation will tell you how to get to the finish you want.
Now the metal has a good surface on it, and I just use Mother's Metal Polish occasionally to keep it looking good. I have found that this is the best product to protect the finish, and it is what my professional polisher recommended. It actually provides a shinier finish than Semichrome. I also use this same polish on the stainless and chrome parts. It is very easy to use.
That's my experience.