If you still have problems, this may work:
Elastomeric SnowRoof watertight flexible roof coating (Ace Hardware). Rolls on easily with long handle. It goes on blue, and turns very white when dry. It took a whole gallon for my 38 ft. roof--thin coat. Solved 98% of the problem with the chalky roof. Much better now.
Jim and Connie, Silver City, NM
2016 Rockwood Ultralite 2608WS
3 lb. Teacup Chihuahua on board