There are dozens of products that will restore the luster to faded aluminum. Depending on your will power and available time, the finished product will reflect both. A high gloss polished finish is very labour intensive, requiring tools and a great amount of determination. There are various sources for these products, avaition, marine, and threads found within this forum.

An easy way to start is just to wash the trailer using a RV product. I've had good luck with WalMart's RV wash, and found it is all I need on bare and painted aluminum.