I was thinking his choice might depend on what kind of new finish he wanted on the item. Automotive paint? A powder coating? Anodizing? Clear coat? Maybe decide that first and work backward to find someone who does it.
Here's a video of a guy doing a home-refinish job on some sort of architectural aluminum, if that helps any. You might want to read the safety precautions on the product labels carefully, but it seems to turn out pretty well:http://www.youtube.com/watch?v=RwNJeOZmvpQ
And here's a discussion of refinishing aluminum when it's parts on a motorcycle. Might have info you can use, and these guys got beautiful results:http://www.hondashadow.net/forum/72-tec ... parts.html