How to paint over a generated landscape material with height and slope blend? PLEASE HELP

I Have created a very simple Layered material for my landscape which implement a very easy height and slope blend, the result it’s quite good but I’m struggling because I don’t know how to modify the result in order to obtain the ability to paint over the generated surface (blending of grass, dirt and cliffs).

To better explain my issue please consider attached pic “generatedLandscape1.JPG”. This is what I obtain when I apply an instance of my layered material to my landscape. I would like now to be able, for example, to freely paint over this result some of the dirt (already blended) to create roads but I have no idea on how to create landscape layers given this implementation.

I went through several videos and guides I simply have no Idea on how to obtain this result. Please Help!!!

Some details of my implementation are attached.

Correct me if I’m wrong, but don’t you still have to layer them with weight blend to be able to paint? (I’ve only mixed in distance blends to fix tiling issues, haven’t done a lot of landscape material work)