Advance landscape painting?

A while ago I purchased the landscape material pack but I have no idea how to apply these premade textures without tearing away half of the detail.

The only way I know to apply them is to create a new material for the landscape and place the 5 I like most (unless UE4 has increased the amount of textures it can handle, please inform me if this is true.) and apply.

These materials consist of a master and a master displacement material. Everything else is instanced.

So the core of my question is, how do I paint on a landscape with instanced materials? Is there any way to do this?

All I want to make is a nice rocky beach that goes into a forested cliff side.

Is there a blueprint workaround I can make?