Poser does not have a Solidify function unlike in Blender3D, so you can't add a toon outline to your celshaded figure. Also, adding a reversed hull geometry adds to the polygon heaviness of the Poser scene, never mind the rigging issues. Therefore, I studied and experimented several solutions by various creators, and have devised hybrid Cycles shader networks which allow me to add my own texture as well, if I need to. Here are my results and my notes (click on the thumbnails to go to larger pictures and discussion notes):
This is my hybrid of the Cageggi celshader with the Will Wenke toon outline shader, and my own shader to add my own texture:
This is my hybrid of the Izzy Fresco celshader with the Will Wenke toon outline shader, and my own shader to add my own texture:
And here are my SuperFly rendered results, which show that despite the difference in shader trees, there is little discernible differnet between the results.