I spent a few hours playing with this technique and finally settled on using coated paper as the substrate because it gave a nicely defined resist image. You can certainly use cardstock or even thinner paper for a different look. Experiment with what you have. You can read the instructions for this technique here!
I used clear wax but you could certainly use what you have for a different look - coloured wax crayons would add a very different dimension to the look of this technique.
I am very happy to have found yet another way to use my embossing folders!!