I tried a few stencils, thinking they might be easier for the kids in my group to learn with, I didn't like the ones I had, paint got under them to much and I could paint it faster than I could fill one of those in. Now Stamping sounds like a good idea, not tried that myself, but if you need to hurry or need an alternative. the little rub on tatoos are great to embelish with paint. In class we all has spiderman, but it was up to us how to paint around the tat. Some were really cool, another item was jewels, one stone with a sticky back, then painted around it , could be made into a ring, bracelet, etc. You can also use the sponges to make some designs quicker, check
www.sillyfarm.com look on the home page, every month she does 2-3 videos demonstrating techniqus or a design.