I like to explore different mediums on a variety of material. The other day at the art supply store I picked up a tin of wax crayons. I had tried them before and liked them. They draw just like crayons. But when you add water with a brush it turns to a creamy paint that you can push around.  It becomes a cross between paint and crayon. When it dries you can add more crayon and can keep repeating the process. I tried using them tonight on dark gray pastel paper. I sat in my truck and colored it in with the crayons and then went back to the studio and used water and brush to fill it in. I liked the gray paper but with it not being watercolor paper it buckled pretty good.