I have those darn black streaks from the roof running down the sides of my camper and my enclosed landscape trailer. I tried this stuff from Camping World called Black Streak Remover, but it just sits there and looks at me. Fantastic from Wal Mart actually works better than the black streak remover! What is it and what can I use on it. My pressure washer is just a small homeowner job. Karcher 2600 PSI 2.6 GPM. Thanks!