Recently I painted my husband's portrait using the same technique and pigments I used to copy a head study by Van Dyke.
Head of a Bearded Man Wearing a Wheel Ruff, by Anthony Van Dyck, c. 1628
Copy of Van Dyck's Head of a Bearded Man by Sadie Valeri
For both paintings, I started by establishing the basic shapes and value pattern with a single umber paint, working transparently.
For the next stage, I painted the flesh tones with a thin layer of opaque paint. I am using Lead white, raw sienna, and burnt sienna for the flesh tones. I also added deeper shadow accents with ivory black and burnt sienna.
Working on top of the wet underpainting, I painted another layer to increase the value range and refine the light and shadow areas. My strokes are short and broken (separated so the under layer shows through), and not over-blended.
The final layers add refinements and detail to the previous layers. Still, I resist over-blending, and previous layers are left visible between strokes.