That's odd. What does it do when you use the brush? Does it not show at all? Are you sure you have the layer above your background and base colors? Are you using a slightly different color than your base?
This is actual a better way to create backgrounds, to make your own brushes that you need for the texture effect and go with that (of course, this doesn't mean go on deviantart and download brushes for the special effects, just make your own).
A lot of people have a tendency to just scribble on the grass, or quick little flicks of the wrist..same goes for hair or fur, I noticed. I've tried that method but I noticed that even if you add breaks for about five hours or up to a month before you get to the rest of your drawing you still end up with carpal tunnel damage from over use of the wrist.
I find this much easier, not exactly "lazy" but just a life savor from injuring yourself from the constant flicks. Thanks for taking the time out for making the tutorial, I appreciate it. It's easy to follow!
I've played around with making my own brushes, but generally I prefer to just work with the ones that come with Photoshop. So far there hasn't been much they couldn't do for me. But I completely agree with you about the individual strokes for grass and hair-- not only does it hurt, but it takes so long!