Every year I try to have different ways to cover our sketchbooks. This was a multi step process.
After gessoeing our covers we glued down paper of music, books or newspaper. Then we used water soluble oil pastels for the background and added water to make it flow. Our image was glued down next and charcoal outlined it.
Some techniques we did were outlining with charcoal, blending with our fingers the water sol oil pastel (dry), brushing water on the pastels and covering the whole thing with a glue wash to seal the color.