Okay... here is a link to download a small test level I made.
termultitex.cd.zip (approx. 2.26 MB)
You'll find the shader_terrain.wdl file that is for ps1.1 and copied from ventilators shader.

The HMP has 3 skins, these are the organic textures.
-Grass
-sand
-cracked earth
The top of the hills will be all grass. Shading into dirt as elevation decreases and then a couple of patches of cracked ground here and there.

The mtlSkin is the blending map with info in the A channel and B channel.
The A channel is blending the grass and sand.
The B channel is blending the cracked ground.

Include the <shader_terrain.wdl> file in your main WDL file.
Assignt the behavior (the action name in the <shader_terrain.wdl>) Shader_Terrain to your model/Hmp and go nuts.

Good luck.
Eric