Today's pairing with thermofax screens is Water Soluble Wax Pastels. I use the Caran D'Ache Neocolor II Water soluble ones but other brands should work very similarly. I am sorry I don't have a link for these but you can purchase them from most art supply stores. The larger ones are harder to find and I am not sure they are even made currently as I haven't seen them in years. They are not inexpensive but they do last a long time.