Photoshop painting help.

I want to create the image bellow and like how can I make the grass on the hills look like they get smaller also how can I have the grass spread out on top? Also can I texture sketchup models on CS4 Extended? thanks. Oh yea can someone tell me where this...

picture might have been taken.

Start making (with small brush strokes in variating shades of green) the blades of grass that are farther away, then start slowly making the blades in order of distance (farther away is first), so the layering of the grass is right.

You may also want to use the smudging (set on about 60%) dodge/burn (set on about 8%) tools to make it look more natural, like when painting hair.

By the way, here's a great tutorial for painting a head of hair (with techniques that you can apply to grass):
http://www.worth1000.com/tutorial.asp?sid=161271

There are a lot of great Photoshop tutorials here, as well:
http://www.worth1000.com/tutorials.asp

Good luck!