Here's a crappy patch I just made from a hand-cut stencil. I placed the patch over a somewhat large hole in a pair of super-comfy, moth-eaten cotton shorts I refuse to toss out, and somehow manage to wear in public without feeling ashamed of myself.
To fill in the patch, I daubed red acrylic paint with a brush through the stencil onto the reverse side of of piece of denim. Unfortunately, the tight lines of the stencil, coupled with the high viscosity of the paint and the rough texture of the denim made distributing paint through the stencil really difficult, so it turned out pretty blotchy and uneven. I had to do a lot of touching up... Would you even know it said "Acid Rain Dance" if I hadn't told you?
It's an improvement over the hole that it's covering, anyway.