bagginsbill (who I think is away for a few days, or he would be here answering your questions I'm sure) has not been able to do a great deal of work on VSS recently, so at the moment it's still free and largely undocumented, apart from a document on his website that covers some of the things you need to know (mostly pulled from this thread, I think), and this thread itself. At 42 pages it's far from an ideal source of information, but it's all we have for now.

I have to say that the skin shading itself is far more realistic in your last render than in your originals. Just look at the gradation between highlight and shadow. Your originals suffer from that excessive contrast between highlight and lowlight that you often see in Poser renders. Did you use bagginsbill's VSS lightset for these renders? You don't really need to, but they are worth a try. They consist of a single IBL and a single infinite, and there are indoor and outdoor versions for different light conditions.

There are two things you can do to alter some of the materials. Either let VSS do its thing and then go into the Material Room and play with the shaders (but they are very complicated); or stop VSS altering the shaders for those parts that you don't want changed. To stop VSS changing certain material zones, the easiest way (I think) is to delete the relevant rule in the VSS Prop. For example, in the attached screenshot, I have deleted the rule lips node, so VSS will not adjust the lip shader. I have never actually tried this though, so you need to experiment a bit!

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)