Do you know any way I can do toon shading while layering textures on top of it?
I am using tutorial for the toon shading: https://support.solidangle.com/display/A5AFMUG/Toon+Shading+with+the+Facing+Ratio+shader). I want to layer other textures (eyes, eyebrows and mouth) on top of it. While the toon shading works by itself, all my attempts to add layers have failed: I tried layered texture or shader but every time my model goes completely black. It doesn't seem to be a problem with the alpha mask. It might be some a problem with using Arnold and Maya materials together. However I'm not sure anymore as I've tried everything that came to mind.
Whats your shading network look like? Why are you using Maya shaders?
Have you tried using the Mix shader?