I don't know if this will add anything to your nodal ideas, but something I started to take seriously regards Specular is something I think of as the "Tarnishing Effect"

You're all sat at a computer, the space bar gets a lot of use, it might have been dull to start with, but do you have a shiny patch where your finger has worn it over time?

The specularity of the material on your spacebar has not changed, but the finish has.  In other words it's the loss of those ultra-tiny bumps that makes it look shiny.  The "specular" of the material looks to have changed, but it hasn't, it still the same material as the untouched keys that still look dull, like new.

The only difference is, the ones that look dull still have those ultra-tiny bumps on them, and I think you might need to differentiate between a "Finish" and a Specular to get your skin absolutely spot on because that's what happens in real life.

I suppose you could say that Specular is the result of a Finish.

To play with the "finish" would involve creating ultra-tiny displacement and changing the spacing between the bumps to adjust the effect of Specularity.  So, maybe set a nice tight specularity and leave it while you play with the finish itself.

Haven't tried it in Poser but it's a very real thing, I used to play around with it a lot in Bryce many years ago, but I was limited to bump and it didn't really work that well.