You can use a lot of materials for this process. The following is a list of things I have found successful. Do not feel as though you need everything on the list, but do have at least a couple different materials to try. Materials need to be water-soluble. Oil and wax based supplies will not work.
Graphite Pencil in 6B, 8B, or 9B
Water-soluble graphite, such at Lyra or Cretacolor Aqua-Monolith
Watercolor Pencils or Sticks
Caran d’Arche water-soluble pastels
Silkscreen, any will work. The 11x14” is the smallest you should go for, Speedball screens are fine.
Paper: Any smooth paper, with weight around 250 gsm will work. I recommend Stonehenge and Rives BFK.