I have only dipped 2 canopies in Future, and won't be doing it again. Future reacts badly with some of the liquid maskers out there. So, I'll just be polishing my canopies from now on like cbaltrin. Its what I had to do anyway on the last canopy I dipped in Future. Gotta love that Novus kit!
I personally don't like going near my clear parts with any kind of sharp, metal object. So, I just make sure to be conscious of the angle at which I'm hitting the masking line with the airbrush. I always am either perpendicular to the masking line, or angled a little bit from the masked side to the painted side so I don't build up a ridge. I never point the aibrush into the edge of the mask and lay down the primer and paint in light, thin passes. If you are conscious of your airbrushing angles and don't have a thick layer of primer/paint, then you can slowly peel off the mask, running parallel to the edge, with the masking essentially being folded back over itself as you pull...then you don't have chipping or peeling issues.
Did that with this F-16 canopy that is several layers of different paints. 1. Decanted Tamiya Surface primer (outside of canopy only) 2. Tamiya X-18 (inside and outside) 3. Remasked outside with shifted placement for simulating sealant strip, then applied Model Master Enamel FS36270 to entire model with canopy temporarily mounted with Blue Tack 4. Masked model and canopy for second camo color, Model Master Enamel FS36118 5. Future clear coat for decals and weathering 6. Testors Dull Cote 7. MRP Super Matt Clear (just because the Testors didn't get it flat eneough for me, next time I'll skip the Testors). Even with all those thin layers of dissimilar paints, didn't have chipping or peeling issues and didn't have to get a piece of metal near the canopy.