Blending Multiple Materials in Source 2 / Multiple UV Sets for Vertex Blending

Hello,

I'm interested in creating some assets for Source 2 and am wondering what the difference is between blend materials in Source 2 and traditional vertex blending textures by height? It seems with the default shader in the material editor that you can only blend two different textures together, when in other engines / 3D packages you could use every RGB channel as well as multiple UV sets. Is there a way I can create a shader that will let me paint multiple textures onto a model? Just having two textures for blending seems a little limiting.

Thanks.

I'm trying to use a lightmapped_4wayblend shader, but am having difficulties. I've created a simple test material with tinted albedos to see if it's working, but nothing seems to happen when I blend. Every channel shows up, but the preview image for each channel looks the same as my base material. The debug mode shows that each vertex channel can be painted, but it looks the same as my base material.

I included an image where you can see the debug mode showing that the vertex channel painting is functional, but the material doesn't look any different.