Update: I just bought a lite-grime-grey (nee white) Haulmark trailer. I tried the Simple Green for Aircraft on it this afernoon, and it works great! We sprayed it on dry, let it sit for about 2-3 minutes, then used a wash brush on a pole with car wash soap and water. Cleaned it up wonderfully.

I even used it on the white (nee lite-grime-grey) tow van and it cleaned up grease I'd never been able to get before...

Good stuff.