Originally Posted by NickTurnon

Buy the "straight edge" painters tape from Hardware Store. Try and tape off the best you can in a straight line. Its best to use the crease that the car has as your line.

Spray a few coats and on the last coat make sure you spray the edges well and get them wet again. Then pull off the tape and paper as fast as you can so it doesn't dry. Do it in the garage or in the shade so you get a few more seconds to peel without it drying..

Theres a couple vids on youtube if you don't understand completely. Trial and error sometimes