Yeah, the "commercial acid" is the way to go. It goes by several different names on the market. Lotsa truckers use it for their aluminum wheels on their semi-trucks.
Be careful though, and WEAR GLOVES AND EYE PROTECTION!!! I'm not kidding! The stuff is wicked bad. It even sucks to breathe it in, so do it outdoors or in a very well ventilated building if done inside. This is more of a summer project rather than a winter one. Anyhow, after acid bathing it and scrubbing the hello out of it, if it's good enough looking for your taste, then you get to quit.
If not, then get out the "powerball" (you can buy them lots of places, for sure at your auto parts store) and attach it to your drill. Buy some Mother's brand aluminum polish, and get to buffing! It's a lot of work, but you will LOVE your trailer when it's all done.
Now for the most important part. If you don't want to do this over and over again in the future, I recommend buying some clear coat paint, and clear-coat the entire trailer once you are done.
The shine will last for years to come, and upkeep will be minimal as compared to leaving the aluminum trailer "bare" as it comes from the factory when new. (Pretty stupid, but that's just how it is.)
Wash and wax after clear coating it all and that becomes the new way of "caring" for the finish! Much cheaper, easier, and safer!
Good luck, and get your wallet out. Chemicals and paint ain't cheap.
If you go through with it, post some before and after pics. I'm sure we'll all like to see your final result!
