A couple months ago I coated the roof on our 96 Southwind. I covered all bad or questionable areas with Eternabond.
I scrubbed the roof with Tide powered laundry detergent, rinse well and allow to dry.
Don't use Dawn or Murphy's Oil Soap, it may cause the coating to peel.
Heng's Rubber Roof Coating was applied, no primer needed. I put two light coats on the roof. It looks great.
I bought three gallons and have about half a gallon left. It covered 30' of roof.
I'm very satisfied with the results. It was easy to apply, it goes on like paint.