I haven't bought the plastic for a while, but there's a plastic you buy in pkgs that you can use to make stencils with. I purchased a stencil burner. You can get both at the fabric store.
All you do is trace your pattern onto the plastic (It's see-through) and then very carefully follow the markings I've made with the burner (It's better to burn on something that you don't care about or a piece of wood) and there you go!!!
Hope this helps!! :-D