What is the best and easiest way to restore the finish on a aluminum trailer?

I spray mine and wipe it with WD-40.

I've never done it myself, but what about taking it to a semi-truck wash and having it washed with the acid solution that they use on the wheels of the big rigs?

SOS pad removes the oxidation if used lightly doesn't scratch. Then some aluminum polish.

the acid at the truck wash will clean the trailer but turn it white over time

I didnt want to use acid for that reason and sos pads would take way too much work....what about sandblasting?

you would really kill it doing that.

All finish wheel cleaner maybe?

I had a Manninig alum trailer I took it apart and had it powder coated.The trailer was painted white and if it did chip it wouldnt rust it was awsome.

myco offers to paint them and it looks real good.