This is an alternative to the chalk stencil
Invisible Children has suggested. With this stamp, you can simply dip it in red chalk powder (available at hardware stores for refilling chalk-lines) and press it on a surface. It should be quicker, easier, and probably less wasteful of chalk than shaking chalk powder through a stencil with a paintbrush. You could also use this technique to make stencils with other images, depending on the size of your foam block and desired image.
You will need a foam block, the stencil template from the Cover the Night Digital Action Kit
, some tape that will stick to both, and a knife. Scissors may also be helpful. The foam block I used came from some packaging
. My parents tried to throw it out, but I saved it because I knew I could find a use for it. It happens to have three holes in the back that make a passable handle.
Don't be stupid like me and make your stamp the same way around as the stencil! Make sure you flip the template horizontally before/when you print it. I'm going to use the extra foam I cut off in step 3 to redo the text. Also, if you use a molded surface of closed-cell foam, you'll probably have to roughen it for the chalk to stick.