Fantastic! A very nice-looking result, easy to accomplish, and non-destructive. Furthermore, it' in my favorite tutorial style, with inline images, which I find very easy to follow.

I do have some refinements to suggest. First, the brush you've pointed out is in the default brushes set, and in the English edition of PS it's called Dry Brush.

Before you create the clouds layer, reset your colors to black and white (D). The clouds will be based on your foreground and background colors, and if you're still using the green from your base layer, it will reduce the contrast of the clouds.

If you would like to smooth the texture a bit, apply a Gaussian Blur to the smart object with a very low radius. About .7 looks good on my test document. Since it's going on a smart object, the blur will become a smart filter, which can be altered later on if you want to tweak it.

If you are using a lightmap of some kind to define your terrain, you can probably get away with turning off the clouds. Since it's a smart object, this is as simple as right-clicking the texture layer, choosing "edit contents" and turning off the layer. When you save, the source map will be updated automatically, and if you decide you want the clouds back, you can edit it again to turn them back on. Also, you can adjust the blending or color of the texture layers at any time with this same method, so you don't necessarily need to choose the best values from the very start.

I think I like this technique better than the one I developed earlier. Five stars and rep from me! Great job!