I used the aircraft stripper (paint remover) from Advanced auto parts. Then I used a buffer and Diamond Brite truck box cleaner from Lowes. I stripped all of the clear coating and decals off. This took the most time (a week off and on). The truck box cleaner took a full day which WAS DONE TODAY.
For a 22 year old trailer that was totally tarnished on the top half, this more than exceeded my expectations.
We appliedthe truck box cleaner with a buffer, let it sit for 15 minutes, cleaned with towels and then one more buffing. See pics.
Note how dull the aluminum was on the entire top half by viewing the far left.
Note that I do not have the finished job because it is pouring outside!