I finally found a use for it the other day, and I stamped up some pieces of white cardboard we had lying around:
First you mix up some acrylic paint and thin it out with water- to about milk consistency. Alternatively, you can use ink- either liquid or from a stamp pad. If you are using paint or liquid ink, coat a roller with it and then coat your rubber stamp.
I had Fen draw any sort of portrait she wanted to at first. Then I had her paint general portrait shapes with watercolor and go back into them later with Sharpie for the facial details.
For the last portrait, I had her choose an animal she wanted to paint a portrait of, and she chose a duck. Quack.
Finally, she decided to add her own little detail in the form of a speech bubble.
This was a fun, quick project, and one that is suitable for use with a bunch of different media. I think it would be fun to try small potato prints inside the frame prints- cut loosely to portrait shapes. Or you could even use the acrylic medium transfer technique.