I've just recently come across a material called Glad Press N Seal that gives every indiction of being an ideal masking material for acrylic paints.
This stuff is a Saran-type material. It is textured on one surface and bears what feels like a low-tack adhesive on the other. It comes in a 75-foot roll and costs a couple of dollars.
This stuff feels a lot like skin, and conforms to irregular surfaces like that material.
I've been building a Tamiya Swordfish and, as is my preference, I've been using Delta Ceramcoat acrylic paints applied with a Paasche airbrush. These paints are well-known for their poor adhesion t plastic, but I use them because they are cheap and I'm indigent.
When masking for the camouflage pattern I used the Press N Seal stuff, and it worked perferctly. There was no "pull-up" or bleed-under at all. None. Zero. Perfect demarcation without any problem removing the mask. Just rip it free and all is good. In contrast to my experiences with every available variety of masking tape and masking liquid, this stuff is easy to use, requires no special prepartion, and will not pull up your carefully applied paints.
All of the moaning I've read about acrylics and the masking thereof encouraged me to share this with the RMS folks. Try this stuff. No more pulling up of your acrylic finishes!
Try this stuff! Two dollars is cheap.