Gaz, For priming and covering larger area, I use my very first air brush - a single action, siphon feed Badger 350 with a medium nozzle. For priming, I've come to rely on Mr. Surfacer 1500 (black); I read somewhere that it contains very fine particles of granite. I won't run it through my Iwata. The Badger is cheap, and mine's been working well for over 30 years.