Yup, been working with my dad since I was 13, almost 12 years now, but expert? No. There are guys in this forum that is more experienced in the helmet/armor painting art. I have not even painted my first helmet yet
.
I mainly do silk-screening work and cutting vinyl lettering/designs using our plotters here at the shop. I dabble in airbrushing as a hobby and sometimes when requested by the customers. I have used frisket , but only on flat surfaces. It's a low tac material so I don't know if it will work too well on any curved surfaces that Fett has, but if you can lay it in strips where the curves are and get a good contact with what you're painting then cut out your pattern, it shouldn't be a problem.
Airbrushing usually minimizes bleeding as long as you do light coats at a time. Airbrushers I know who work with helmets usually use masking tape(Only if the paint you're putting it on can withstand the adhesive without peeling off)
I personally use latex rubber (you can buy at any hobby store) as a brush on masking for the models that I have done and it works great. This is probably the way I will do my first helmet.
Just my two cents.