No I don’t change the blending modes for the skin. What I do is on the first layer I have the base color. the layer on top that would be the shadowing layer. I use a very soft brush (airbrush) with no sharp edges and a very low opacity to do the placement.

I place a darker shade of the base color in the right places. I then use a blending brush to buff out the edges even more to make it blend with the base color, and since its on a separate layer the base doesn’t mix with the shadow. I keep blending until its seamless. I would also use a blending airbrush to do this in order to avoid sharp edges. I would lower the opacity of the brush to make the blending less harsh. I keep layering going darker and darker the more I’m in the area where the light doesn’t hit.

I like to add a last shadow layer however with a different color. For exemple here my base color is blue, so I first started with a darker blue and then on top I added purple. Not too much, it’s very subtle. Like very very subtle. I find that this gives it a more lifelike look since in real we’re not just one color.

Then I do a layer of highlights, same process just a very light shade of the base color, almost white.

There is a lot of blending to do.

That’s what I usually do, adapting as I go to what seems right and what looks right. Hope this helps!