I just can't tell you how much I love your style. So much so that when I saw these "process" photos, it hit me that you had a process. Not kidding, I kind of thought you were magic. Your grasp of the planes of the face is something I can see in my mind but can't reproduce. Props. Just props.
For portraits, I use mostly earth tones, olive green, raw umber, burnt umber, alizarin crimson, burnt sienna, mars yellow, and I add to that any colors I might need depending on the circumstance. Brushes depend on the size of the area I'm painting but I usually end up using something about 1/2 inch, 3/4 inch and maybe a 1 1/2 inch or so.