Do you want a regular grid of dots, or randomly spaced (randomly
sized?) dots?
Mark out carefuly what you want with little pencil marks or bits of
masking tape, figure out what you will do in difficult bits around
doors and windows etc.

Whatever you do, practice on some old paper first. For sharp edges on
stencils, I find spraying works well (any cheap black spray paint
should be fine). Not sure about the template, try thick card?