I drew the masking template freehand on semi-transparent graph paper. I traced the wing outline first, then drew the camo "squares" and cut them out with a sharp exacto. After that was done, I flipped the template over and stuck small thin pieces of Blue-Tac in between the camo shapes and at the template wing edges. Then I simply flipped the template back over and stuck it to the wing - I only had to use a little pressure at the wing edges to make the template was secured. Once the template was on, I simply airbrushed away - making sure that the surface of the wing was perpendicular to the paint spray to prevent underspraying between the wing and the template. (The only time I altered that was when I did the slight wrap-around on the leading wing edge.) When the airbrushing was done, I carefully peeled off the template and removed the blue-tac. Any pieces of blue tac that wouldn't come up off the paint I removed by simply rolling a little ball of blue tac over them.
Here's the latest shot with all three colors on the main and rear wings. Needs a bit of tweaking still. Not sure that this one is going to be done in time.