masking fluid and scrape my thumb across the toothbrush to spray the fluid in certain areas. The masking fluid protects the paper from the ink. I also dip my quills and brushes in the masking fluid to create what will eventually become white lines on the page. It's almost impossible to find a quality white ink that's easy to work with, so this is just an easier and faster solution for me. Once I'm done inking the entire page, I can just rub off the masking fluid to reveal the white paper underneath.
you can grab those brushes here. Sorry, but I offer no assistance on using or installing these brushes except that you should only click once to create the spatter. Dragging the brush will not work properly. Hit Google and look for some Photoshop Brush tutorials, they'll have a ton of helpful info.