This is a crayon resist project. Basically, you let the kids draw a picture with crayons and then they paint over their picture with paints. Since the crayons are waxy, they resist the paint (giving the technique its name), and the drawings will come through.
Step one: trace a dinosaur skeleton onto your white paper using the print outs as a guide.
I used a white crayon for this step, and while it worked, I would suggest using oil pastel instead. My crayon did resist the paint some, but in the end, it was a little difficult to see the skeletons.
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Update! I let Natalie try this project after she came home from school and cautioned her against using too much water. I told her to get her brush wet, but only just, and to really load it up with color (most of the colors were still wet from this morning). The result? MUCH better!
So, I guess white crayon actually does work pretty well. The trick is to not transfer too much water to your paper...and to take the art away from the child before it becomes a wet puddle!