I usually use Tamiya tape to mask my models, but since I only brushpaint (no airbrush), I ALWAYS see a lot of paint going under the paint and ruining the other paint job. Any brushpainters out there with any masking tips?
Be sure to burnish the edge of the tape down. You’ll know it’s burnished when the tape turns slightly opaque. I also use a liquid masking agent for some masking jobs, Hobbyco puts out the best one that I’ve ever tried.
what do you use to burnish tape down? fingernail? some blunt tool? a ruler?
You can get special burnishing tools at art supply stores, but in most cases a fingernail works just fine. The burnishing tools have a round ball on one end and a flat “Spatula” on the other end. They work pretty well but I usually just use my fingernail.
You can also try putting a coat of clear along the edge of the tape. Future would probably work fine. If it seeps under the edge of the tape it usually isn’t noticeable.
One word of warning … I’m sure you already know this, but the harder the tape sticks the more likely it is to pull up coats of paint that are already there. This is especially true if you use acrylics without a primer. Make sure the underlying coats are fully cured or you may pull them up along with the tape!
Tamiya tape is good stuff, the best in my opinion, but it is considered to be “Low Tack”. I’ve never had any problems at all with it, but I usually airbrush most things.
Thanks! I’ve never had Tamiya tape pull out any paint, though. 
I usually use the sides of my tweezers or fingernail. Depending on how tight the area is, sometimes a toothpick. Anything will work really, as quoted above, “slightly opaque.” You’ll know when it’s there.
That’s only because you let it dry longer than I frequently do! Impatience is not a modeler’s friend. [8D]
ditto what the other guys have said. I would add that your paint brush must be almost dry when painting against the masking tape. Takes a little practice but will keep bleed through to a minimum when done right.
Mike McShea
As a former professional painter(residential and commercial), I can tell you that any brushing over masking tape is a big no-no. You would be very lucky to not have some, or a lot, of paint under the tape. In modeling, one might burnish the tape well enough to prevent this but I would be hesitant to encourage this method. Gary