Mike, I use a product called On & Off, this stuff is powerful. The directions say to cover the trailer so you wont spill any on it and EAT the steel!:eyecrazy:
I use a small, disposable paint brush, apply very little, wait about 3-4 mins. and hose off. No scrubbing at all. I'm not sure what is in it, toxic don't come close to what I fear, but this stuff works to beat the band.
Now, if I could come up with a similar product to clean the mold from the deck(darn shrinkwrap and no ventilation does it every year)I'd be on the water by now!
BTW, you can get On & Off at most marine stores!