Eduard's die cut masks work nicely, but you have to think ahead and order. As blitzwing mentioned, scotch tape works very nicely and allows you to see where you have to burnish down. I've not had much luck with liquid masks personally, and I've never tried bare metal foil but I've heard that works like a dream. The thing I've found with bleed under is sealing the edges first works out well. After taping, a quick brush layer of gloss around all the tape edges will form an invisible seal and prevent bleeding, and if the gloss bleeds under, no big deal as it just looks like canopy glass. Usually, painting the interior color first (as it will be seen inside) then other layers over that. It's pretty difficult to mask and paint the inside of the canopy.