Contact Kenneth at Grandview Trailer Sales and order some Reliable RV Cleaner. Use it fully strength to clean the RV and then Wax it. Use a good fiberglass finish restorer/wax if your RV is fiberglass. Lots of work.
Like Dennis said...TOTALLY AWESOME from the Dollar Tree works really well on black streaks, mold/mildewand other stains on the RV. I try to avoid the Citris based ones. It does remove wax finishes though. We have a rubber roof and I have tried several over-the-counter products. What works best for me is a 50/50 brew of Spic n Span and Murphy's Oil Soap. After our rig is clean, I generally put a coat of Protect-All on. Probably not as good as a quality wax but a lot easier!
I just have to say I agree with all the statements above. I also use the 50/50 solution on my roof. It seem to work fine for me. I use newfinish wax on the out fiberglass. and I always use armorall on the wheels.