One of my favourite techniques, because it always works out well, is to emboss in white, spray with water, sprinkle with Brusho and watch the magic happen. You can manipulate the Brusho by spritzing with more water, moving it around with a paintbrush or lifting it off with a paper towel. Once the first layer is down you can drop in more to deepen some areas. To finish off use a fine black pen to outline and alcohol markers to colour small areas. Finally a few spatters of paint to tie it all together.