Tamiya masking tape and adhesive-backed foil (such as Bare-Metal Foil) is thin and works well. My favourite is the Tamiya masking tape.
First cut the tape in thin stripes and place them against the frames, then mask the rest between the stripes taking care to overlap them.
After masking I spray the interior color of the canopy frame on the outside and follow with the exterior frame color. This is easier than trying to paint the canopy inside and out. Remove adhesive residue with alcohol on a cotton swab.
One more tip: Dont forget to mask the inside of the canopy to block overspray.
Painting bombs without decals:
The problem with painting rings on bomb noses is masking a sharp line on a compound curved
Masking with tape or applying solidcolor decal film doesn't work well because you're trying to apply a flat material to the cun'ed surface. To resolve this, first, paint the front end of the bomb gloss yellow and allow it to dry. Then apply a liquid masking agent over the yellow and let it dry. Next, carefully chuck the bomb in a variable-speed electric drill (don't turn the chuck too tight or you'll crush the plastic.) With the drill operating at low speed, bring the edge of a sharp modeling knife (Xacto blade
nº 10) to the front and rear edges of the area to remain yellow, cutting through the masking agent.
When done, peel away the masking agent at the nose tip and from behind the yellow ring.
Paint the entire bomb olive drab and when dry remove the masking agent from the yellow ring.
The best way to mask a circumference is to use frisket paper, sometimes called frisket film. This is a thin, paper-backed, selfadhesive material used by artists to mask airbrush illustrations. Look for it at artsupply stores. You can use a draftsman's compass with a cutting blade in place of the pencil.
First, cut the mask for the outside of the circle. Then cut another circle smaller in radius. Apply the frisket outline on the part to be painted, then place the smaller circle within that mask, making sure it's centered. When you're satisfied with the position of the masks, burnish their edges with your fingernail.
Now you are ready to paint, preferably with an airbrush. If you hand brush, take
care to keep the paint from creeping under the frisket.
Let the paint dry and remove the masks.
Instead of using a circle template to cut masks, use the template as a mask.
Paint the tire black or dark gray with an airbrush and let it dry. Now prepare the paint for airbrushing the rim of the wheel.
Find the circle on the template that is closest to the corrcct diameter of the rim and hold the wheel behind the template, only the rim must show through the template. Spray through the template; remeber that you may have to cover the adjacent holes in the template.