I had some black streaks on my fiver after a the rain and dew. I used Mother's cleaner on it. It's been about three weeks since I did it. We've had a few days of rain and dew every day it hasn't rained. The area I used the Mother's on still has no streaks.
It can be found at most stores that have decent selection of auto accessories. It's a three step process to do it right.
To apply it is just like waxing the rv. Put some on a soft cloth. Wipe it on, then let dry to a haze, then use a soft cloth to buff to a shine.
I still have to try it on the front to see if it will help with cleaning the bugs off.
My fold out door grab bar leaves a black mark/streak from the black foam grab. While I was washing the TT yesterday, I though about using some SoftScrub. Tried it and it worked great. Also I use clothes pins on the gutters. Too cheap. Anyway one fell off and I got a blck streak on one side. Tried the Softscub on it and it worked great as well.