Thanks for the tip, EJ122763!
I've tried multiple brands of RV "black streak removers" and have found that the best product(IMHO) is something called LA's Totally Awesome. LA's Totally Awesome Products
I found it at a Dollar General up the street. It's $1 for the large spray bottle and $3 for a jug. I spraw it on, wait a couple minutes and effortly wipe it off with my car wash sponge with some soapy water. It wipes right off without any elbow grease. Then hose it down. It cost me $2.50 to remove a winters worth of black grime from my 26TBUD sides this Spring. I really need to get that thing covered in the winters!