I suggest Bob Divley's Liquid Mask Film (LMF). This is what the Pros use (Doug Summers aka BODZ and several others). If your hobby shop orders from great planes (most do), you can get a small or medium sized bottle for not much money.
You're supposed to apply it with an airbrush, but it's not needed. Just grab any only bristle brush and apply a light coat. Use a hair dryer to speed up the drying process and then apply another coat and repeat. After you have 4-5 light coats, it's time to cut. The more lines you cut the longer this process will take. To make things easier pick up a box of brand new exacto blades (you'll be glad you did).
Now the idea is to cut a shape and peal back the LMF so you can paint under it. I used 1/8" pin striping on the inside of my lid to act as a guide line. You apply the LMF over it and cut right next to the edge created by the pin striping. (EDIT: you remove the pin striping and don't paint over it)
Just plan carefully, take your time and you'll have a sweet lid in no time. I suggest you start off simple. It's a real labor intensive process.
I used Bob Divley's LMF, Parma Black, Yellow and Red rattle cans to paint my latest lid (see attached image). The pin striping really helps make those even black lines if you want them. You can also cut just on one side and use it as a guide.
PS. yes I know I painted the windows so it's not ROAR legal. blah blah I just club race anyway.
