I ma finding when using acrylics I can airbrush but if I stop teh next pass shoots out a couple of drops of paint. What is causing thepaint to build up at the tip? I have the iwata hp-c and the aztek 470 which is the main brush. I think this has more to do with the paint I think. any suggestions?

Paint is collecting just inside the nozzle as you paint and when you apply the sudden air pressure it spatters out. The best thing to do is point the ab away from the part and just let a short blast of air blow through to clear it out before you start spraying.

There's no substitute for practicing the use of your airbrush. Like knowing how much pressure you put on the trigger when spraying. And like what was mentioned before, start painting at the edge of your model and steadily work your way across the model until you reach the end.

Would say pressure to low or as Twisted fate said clean that puppy!

Also another thing with this kind of paint try a drop of liquid soap kind of keeps it from sticking so bad and clogging.
I really don't like Acrylic that much cause of this fact clogging real fast.
Thinking of heading back to good all Model Master paint!! never had a problem!!