I clean my roof once a year with EZ House wash. Follow instructions. Spray it on wait 15 minutes, rise if off with lots of water and hose down the entire sides / coach. It removes, dirt, stains, mildew, etc. Only mild scrubbing may need to done. I've used this stuff for years and works great.
You can get the product at Walmarts in the paint department too.
https://www.walmart.com/ip/Home-Armo...E&gclsrc=aw.ds
Before I was on my hands and knees, with bleach and soap but never removed the stains from trees and berries. Also I would NEVER use a pressure washer these things are destructive!
Good luck,
John