I bought a Proshot to spray my interior doors in our new house. Yesterday my dad sprayed seven of the doors. He said it took 2 1/2 gallons for one coat! That is using a 211 tip, BM Satin Impervo Waterborne. He said it took forever because he had to refill the cup so often. I am think he might be spraying too slow. I have watched videos on youtube of people spraying a door in 30 seconds with the proshot. Any thoughts? I have a 411 tip also, should I try that?