Here's a look at what I'm currently working on. You can see some pieces of string and thread I've coated with frisket and stuck onto the surface of the paper. I'm masking out areas that will later become blades of grass. When all the background work is done, I'll pull off the string and rub off the frisket, and then paint in the lighter-colored grass. Since watercolor is, for the most part, transparent, I have to resort to this kind of trickery to depict light objects in front of darker ones.