I am having some airbrush problems myself I just posted about, but I used to have the same problem, especially with rattle cans. Very light coats built up fixed it for me, but only with my airbrush. Also, using good quality masking instead of thick tape helped me a lot. The paint will stick to the edge of the tape, so if its thick, it built up a thick ridge for me. I now use Para film or Tamiya tape, again, very light coats, with a Aztec airbrush. Hope that helps.