I'm also trying to force myself to ZTFO (zoom the f*** out!) as much as possible. This study looks pretty awful zoomed in since it's still very rough, but it seems to read pretty well from a distance I feel. My usual problem is trying to "render" things rather than paint the impression of how they actually look, from the correct distance. This usually involves zooming in, rendering, being happy with it, realising I forgot to zoom out at all, and then seeing it for the mess that it is once I do finally ZTFO. Lesson.. ZTFO! and do so often.
It also hammered home the point that the saturation of the warms is very restricted since the ambient light is cool. Even the most saturated scattering in the skin is still pretty low saturation. Another mistake I tend to make.
A pretty massive revelation to me fairly recently was to simplify planes far more before any sort of blending happens. I wasn't doing this anywhere near enough and it makes a huge difference. This, along with the zooming, is very high on my list of stuff to hammer home at the minute.
Another thing made obvious to me was that my hard edges are too hard. Looking through high end CG caps, even static shots, there are very, very few edges (if any) which are as hard as a hard round brush.
Lastly, to add a little texture I used a very low exposure textured dodge brush is some areas of the skin. This was to add a little bit of texture and also to quickly add some slight variation in saturation. I feel it works really well when zoomed out, although it seems pretty dirty close up. Maybe just a case of being less sloppy or tightening things up a little more?
I know studying from life is important but in my experience studying CG is also extremely useful. It's cinematic and readable in ways that life is very rarely close to, and the lighting is controlled and simplified where the real world can often be ambiguous and over-complicated for the sake of learning. I hope this has been useful to someone.