Yesterday morning I spent some time going through Twitter and following links. Which led me to this cool idea on Paula Phillip's blog - ghosting - using gesso and Ranger's Color Washes. Check out her blog post - she's got a good video demonstration.
Basically, you start with a black gesso background. The paint is key. I tried it on Ranger's black tags and it didn't work. I should try a plain black paint background and see what happens....
Then, stencil and/or spray with Ranger Color Wash. After it's dry -- really dry -- you can go over the top with white gesso. The colorwash will come through the gesso.
Here's an art journal page with this technique. Love how this turned out!