I used Mule 300 on my motor home rubber roof water based drys like a rock. It is made for use on rubber roofs and is considerably cheaper than the RV sponsored products. Motor Home is 36 feet and it took about 2.5 gallons, I bought a five gallon container and used the rest on my metal roof on my sun room.
I washed the roof with Dawn liquid soap rinsed it well, allowed to dry. Went around AC units, seams, and any thing else that looked to have a seam or crack with a brush and applied coating by hand, after drying I used a sprayer I lightly wet the roof with a mist as I went, helped considerably applying the first coat. I used a medium nap roller and a roller pan and rolled on one coat working from front to rear towards my ladder, Waited for first coat to dry over night. Next day put on a second coat repeating first step coating procedures. Do not wear shoes when applying second coat has a tendance to scratch first coat. After drying it looks great. Hardest part was preperation and first coat took about 3 hours early morning, second coat took about an hour.