Dave,

What Barry said.

The 3M green is a low-tack, very clean tape that will work well for those Mylar aileron gap covers. But I wouldn't run out and buy a roll of it just for that -- any moderately low-tack tape such as hardware store masking tape or black electricians' tape would be fine. (Lay it out on some waxed paper and cut it with a razor & straightedge if it's too wide for your aileron strips.)

For trim colors, where you may have curves and certainly need a good seal, there's nothing better than the 3M blue, 1/8" wide. Lay out the edges with that, then follow behind/over it with 3/4" wide masking tape and Saran Wrap or butcher paper for really large areas. I like the Saran Wrap because it clings to itself -- you can wrap it & bunch it around your tailfeathers, for example.

D.