I have had some luck by doing the following...
My wife has a cricut machine.
I stick some Frog Tape down on the cricut mat.
I use some spray adhesive to stick some paper over this.
Then, I have my wife cut the design on the cricut. You can use this as your stencil.
However, the model master paints seem to have a hard time and it messes up the paint. I have some success with model master paint using "delicate frog tape" the yellow stuff.
I've heard one of the keys though is to spray your color. Apply your stencil, spray base again to seal the edge, then spray your stencil color.