Personaly I use a decent brand of masking tape, and sometimes the cheap ones work ot. Either pick up Automotive masking tape or stuff designed to be applied to fresh paint on walls. It is sometimes hit and miss, if the stuff isn't very tacky then I use it to fill areas and then use decent tape along where the masking lines go.
If you can get it, Scotch 3M Blua masking tape is excellent, only down side is it is harder to see through to cut your pattern.
Liquid Mask, Bob Divley is the best, nobody stocks it in the UK but from what I here you got to apply a good four to five coats, the thicker it is the easier it is to lift off the shell. But it will eat through the blades to.
If you need any help let either me or Jim know.
http://academyracer.fotopic.net/c922689.html
I also do a lot of freehand work in the designs to.