A laser cutter can conveniently be used to directly cut stencils in masking tape or pretty much any tape. This tape can then be stuck to your surface, spray painted, and removed. I used this stencil to personalise the bicycle i was building for my ladyfriend.
Step 1: Lay out the tape on your laser cutter bed and set the correct focal distance for your laser cutter.
Step 2: Design your stencil, I used corel draw and used a basic font suitable for stenciling.
the thing about choosing a font is choosing something where the holes in the a's and b's and d's and o's and p's don't fall out. I used the BAUHAUS font for this bike.
also make sure to convert your font to an outline so you only cut the outline.
I've attached the illustrator and post script files.
Step 3: Cut your stencil. typically low power setting as tape is thin. I used bear tape for this stencil.
Step 4: Carefully orient your stencil to the object you are painting.
Step 5: Press your stencil close to the object you are painting.
Step 6: I use an extra sheet of card to prevent overspray, and to receive the splotchy first second or so of spray from cheap spray cans.
Step 7: Starting with spray on your overspray card, move to your stencil area giving a few light coats.
Step 8: Ta-da. allow to dry. I used rust-oleum. works great on a lot of surfaces and is cheap and easy to get.
Step 9: You can see from this detail that it requires a second coat.
Step 10: After it is dry carefully peel back the stencil.