Another user of Slimy Grimy. I mix the powder with water in a garden sprayer and spray it on and the stains just disapear. It is pretty costly but it sure takes off the crud.
I did notice it can spot metal or unpainted parts on a trailer if not rinsed quick.

Cordell

There is a product called slimeyGrimey, and it is not as harsh as OnandOFF works real well with stains.....

Check ebay thats where I buy that slimy grimy it's alot cheaper..

Just be carefull with any of the On/Off's and stuff if you have a alluminum or galvi trailer. The stuff will attach it. Make sure you wash everything off REAL well after you are done. I guess you could spray everything down with TUMS when you are done

sno bowl is the best ive ever found....just swipe it on and the stains dissapear