A trial with some left over water based printing ink. So roughly done I never expected anything to come out out it.  Firstly drawing a figure with charcoal tinted pencil in the page centre and then rolling the brayer over the top, this way and that, it created much more movement and (for me) a more interesting background to journal on. The brayer picked up the charcoal and echoed the lines elsewhere on the page. Not sure this is controllable.