This is my approach to painting a face in my illustration work. It’s definitely not the only way to do it, but it works for me. This is similar to the same approach taken by a lot of golden age illustrators to whom I look for inspiration. I start with my photo reference (which I always convert to black and white as to not be influenced by the color of the photo),
The white outline is chalk pencil drawn over dry paint, to loosely block in where the figure will be. The paint lay in is the darkest darks, the eyes, etc. I then lay in the shadow shapes, not worrying about likeness or edges, keeping all edges hard edges, or “tiling” it in. Then the basic flesh color fills in the mid-tones, and then the hi-lights. I then start the whole process over again with the darks and now start looking for likeness as I define shapes and soften edges as needed. Colors used are oils: Titanium white, burnt umber, yellow ochre, alizarin crimson, cerulean blue, ultramarine blue.