Frisket film works on tissue that has been doped, at least for air brushing. It's a little stretchy, so it lays down nicely. It's expensive ($2 for a letter size sheet) so I usually just cut a narrow piece for the edge, and use paper to mask larger areas.

Marc - I've tried several methods and the best for me is Washi tape. I use the 1/4' width, anything wider than that gives too much area and will tear the tissue or lift the paint. It is a bamboo base and very flexible with light adhesive and get it at Staples or Michaels. I use it to outline the areas to be colored then use blue frog tape on newsprint with a bit of overlap off the newsprint and stick that to the Washi tape just to prevent overspray. Not sure how this will work with hand painting.
Mike

Marc,

I've had good luck using yellow Frog brand masking tape over tissue and on props.  It's available at Home Depot.  For tissue that's already got a coat of paint you'll want to stick it down on your forearm once or twice to reduce the tack, otherwise you may pull up bits of paint from the underlying surface.

If you're airbrushing paints like Tamiya acrylics onto doped tissue, try using lacquer thinner as the thinning agent.  I found it made the paint bite harder onto the doped tissue and gave me less issues with tape pulling up the paint on subsequent colors.

My experience with blue painter's tape was that it stuck too aggressively to be safe on tissue.


Mike