For other painters out there. You may have to be certifiably nuts want to try it, but there's a couple nice write ups on how to paint grass like John-Howe,
John's explaination, and a nice visual tutorial someone made from it.
I get the urge to do it every once in awhile. I do not really follow the tutorial since I hate masking fluid. It's fun and aggravating at the same time, but really satisfying when done right. This time it's not a commission, but the grass is the most complicated thing in the picture.