if you want to get layering to work. Then just use the layered texture and paint the alpha channel with another texture.
(look in help files)

UV snapshot out your terrain mesh and paint alphas for where you want your different elements to show up.

A quick fix to do this is for example if you want different textures applied based on the hight of the geometry, to do this you can use the snow 3D texture to drive the alphas. To get a higher resolution you either just paint your maps higher resolution or you can tile your textures using the place 2d node attached to your procedural or file node.

How that makes sense, if you need a more detailed overview, ask.