Bigfoot dirty water streaks down sides from roof, solutions?

Anyone used Wet & Forget on a RV? I've used it on the rubber roofs of the previous Montana and the TPO roof of the Landmark.
I had a Classic Industries cover on the Bigfoot for quite a while. It developed a light mildew. The area between the back of the A/C and the rear skylight had more mildew and **** on it. It's a pretty tight area to access and I've been thinking about spraying Wet & Forget in there and maybe the entire roof.