OK you're going to have to explain what you mean by "paint masks" Stencils in theory are typically cut out of cardboard and simply laid on an object before spraying to get lettering or some design on the surface.
Steve
I get my paint masks made at the local sign shop, Pit Stop Graphics.
According to my man, stencils are reusable and a made to stencil many units.
Paint masks are a one time throwaway mask.
The masks I buy involve three layers. The mask is in the middle. The backing is in back. The lifting tape is in front.
You peal off the backing and remove the part of the mask you don't intend to use. For a number, for example, I remove the numbers and save them for a future project. They are stuck down to an old piece of backing.
The lifting tape on the front keeps the whole mask aligned until you apply the mask.
So you press the mask onto the model and run it down with the lifting tape in place.
When it's rubbed down you peal off the lifting tape and spray.
Then I can do a future project by painting the number color first, then hand-aligning the numbers between masking tape.