I experiment with shading techniques often ever since completing a dragon picture where I followed a shading tutorial for photoshop artists. Before I was a big fan of the soft edges brush where the hardness was set nearly to 0%. I’ve found that that isn’t necessarily how all shadows are blended on the skin. Now I will change the hardness of the brush when shading at intervals and experiment with the effects. You can see the difference in the ‘harder’ shading at the face, neck, and arms versus the ‘softer’ shading on the legs of the young woman in the picture below.
I’ve also been learning how to add different pigments when shading. Sometimes I have to change hue and go to the opposite side of the color wheel to make sure I’m doing things correctly. The picture below isn’t necessarily one of those examples but it shows the start of one of my preferred skin shading techniques. For this one I also color dropped from a photo and added more fleshy toned pink to places where the blood vessels may be closer to the surface of the skin.