The best way that I've found is to use is the "Cartoon Shaders" material pack from RDNA. It is well set up to allow for rendering in a number of cartoon styles (anime, 4-color comics, more modern comic style), and can incorporate existing textures with cartoon style shading. It has a pretty good tutorial as well. It essentially bypasses the Poser Cartoon rendering entirely.

I also use ShaderSpider, available form DAZ, to help apply the textures to just those groups I want. (On the Millenium figures, it knows what material zones are skin and what aren't.)