If you install the samples, have a look at the brick wall. You can see how they've added in some pretty good noise on the bricks and the mortar, plus there is some really nice masking going on.
I started with a nice chewed up brick that was tapered on the left side. This prevented the bottom corners from touching when the brick was copied around in the splatter circular. Next I added a transform 2d so i could rotate the circle of bricks and have control later on on which color variation was where. Then another…