Thank you all for the kind words, I'm glad you all like it~
As to your question, JerseyDusk, I started out with the rough shape I wanted to be grassy, then did a solid gradient because the next step can leave some semi-transparent spots behind otherwise. I'll take the soft brush pencil tool, and using low opacity, high spacing, and very low scattering settings (image to the left is of the ones I used for the demo piece), go over the area with multiple shades of green to block out what areas should be lighter and darker. Lastly, I'll take the smudge tool, size it at about 4 or 5, and just use a series of quick, short strokes to go over each colored blot, beginning from the top and working my way down until I reach the bottom of the frame. Used higher contrast colors in the demo piece, but the main shades of green I used in the above cat piece are;
███ #384d34███ #637d5b███ #89ad6f███ #abc395