Sorry but you aren't going to get something that looks like that from a pressure sensitive brush in Illustrator.
The colors and groupings of blocks are too random to be a repeating pattern (a simple one, anyway) and the order is too consistent to be something like a scatter brush. That said, you *can* do this with a brush but it won't be pressure sensitive and it will require a degree of setup.
Start by building a row of blocks. Mine is a simple pattern with a few pieces removed and not terribly interesting looking but hopefully it'll give you the idea of what I mean:
Group everything and then go up to Effect> 3D> Rotate
Set your X, Y, And Perspective parameters to taste. Keep the Z axes (the blue one) at zero:
Go to Object> Expand Appearance You'll notice that Illustrator has put a clipping mask around your squares (transparent rectangle) Delete it.
Take everything you have and drag it over to the brush panel and make a new Art Brush:
Now you can select that brush and paint with it though you'll get better results by stroking a path you've drawn with the pen tool:
A couple of things to keep in mind:
You'll need to consider your ultimate length when creating the brush. Longer or more wavy lines will require more squares. My squares look a little skewed because I didn't bother to make my pattern very long. A longer row will improve the look of this but hopefully my example is enough to give you the idea.
For generating the square colors, you might want to try the random fills script available from James talmage's page and then use live color to tint everything for you.