Thanks for the responses.  I've actually figured it out.

David, you're right, just rendering with the Toon!pro on does give a toon-like effect -- mostly the outlines -- but there is also a toon shader function that reduces the shadows on the toon character to much simpler levels.

It's done like this:  Open the shader for the Poser character in the Shader room.  When the shader is open, create a new master shader (using the pull-down menu) and set Toon Pro Cel for the top-most shader.  Then, select the layers list of the shader for the Poser figure.  Copy this.  Paste it into the shader for the new master shader, under the Toon!Pro Cel.  Then, select the top-most shader of the new Master Shader.  Copy it.  Select the Poser Figure's shader and paste the Toon!Pro Cel shader onto the Master Shader.

It sounds complicated, but once you do it once or twice, it makes sense.

 - Dex