Fade technique?

[Monkeysmate]

A while back I posted up some pictures of a shell I'd painted, and comment was made that I should improve the fade when using a small dot mask.
I would be grateful if someone could give me any pointers on how to achieve said fade?
Is it a matter of several thin coats? Or do I need to be using the airbrush trigger to reduce the paint flow? Do I spray across the fade? Or along the fade?
Sorry for all the questions, but any advice would be gratefully received.
Thank you