Bleach and dishwashing soap. Scrub it on, let it soak, then rinse while scrubbing some more. Repeat as required. Be careful to keep it out of your eyes and off of any decals or paint on the RV - that's why I never rolled my awning back up to let it soak. So, I kept it off the RV, but don't ask about my eyes!! :{ :{
Rusty