The title pretty much says it all, but yesterday I was marking my territory (large tools at JaxHax Makerspace) with an electric engraver I picked up from Harbor Freight for about $8, and noticed one of our members making a spray paint stencil. It occurred to me that the engraver might be a good means of speeding up and easing making that stencil as opposed to using an exacto and a steady hand, so I gave it a whirl and I'm happy to report and it's great! As quickly as you can draw around the edges of a stencil with a pencil you can make it with an engraver.
Step 1: Tools
1 - electric engraver. http://www.harborfreight.com/electric-engraver-46099.html
2 - stencil pattern printed on card stock
3 - backing plate. Either steel, wood, cardboard, etc... The harder the material the better. Don't do it on a surface you're not okay with marring.
4 - tape
Step 2: Cut It.
Tape the corners to the plate and run the engraver all the way around the stencil. I usually remove parts of large areas rather than the whole thing at once, and make sure youre letters' islands have supports. Oh yeah, wear headphones, this part's loud.
Step 3: Tape and Spray
Remove any leftover cutouts and then test your spray out. Be amazed how easy small detail is to keep cleanly cut and how much faster you've just cut this out vs your xacto cut stencils.
Step 4: DONE!
Pull the stencil away and admire your work. Only do this on walls you have permission to do it to.