I use the frisket but for some projects I just cut through thin plastic to produce a template or pattern than I can spray through. The advantage of the Frisket is it leaves a very crisp line because it's stuck to the wood. The templates are taped down and if the wood is slightly curved will not lay perfectly flat. They do sell stretchable frisket for shooting on curved pieces. I've seen that in catalogs for painting motorcycle parts.
I have just started playing with spray or brush on frisket but had terrible results with the early products I tried. I just purchased a new product but have not had a chance to use it yet. My problem with the brush on Frisket so far has been getting it back off. Since you brush it on, let it dry, cut out your mask and then remove the mask, this is kind of important. I'll let you know once I get a chance to play with the new stuff.