During our fall stay in PA, I went to a couple of two hour live portrait sessions at a local art center. On one occasion we painted a class member and on the other, a veteran. There were 6-8 artists present, using a variety of media.
On the first session I attended we painted a class member. I started in charcoal, and was pleased to find I could make a decent likeness in about half an hour.

Then I painted the sitter again using a very limited palette of oil paints. This was yellow ochre, cadmium red, ivory black, titanium white and transparent red oxide (a modifed version of the palette used by Swedish master artist Anders Zorn).

I started with a very rough block-in, then painted all the shadows with transparent red oxide for the face and ivory black for the clothing. I found the limited number of colors easier to manage and mix.
I was very happy with the glow that the red oxide gave to the face. The other class members had useful comments to make about my efforts and said I’d captured his likeness exactly. It was all very enjoyable and satisfying.