PCG mask painting?

Hey all!

I’ve been searching and trying out some things with no luck so far. I have created a GPU accelerated PCG template for creating grass. I would like to paint out areas where I do not want any grass to be visible.

I have been playing with my Layer Blend material with my landscape to try and create a mask layer but I am missing something. I am not too sure how to hook this up to my PCG and get all the pieces together. Any help would be greatly appreciated!