Trying to paint Portraits is always tricky. Besides getting Facial Features, Proportions and Expressions correct, it takes Tones to pull it all together.
So, me, in my impatience and laziness, I try and start simply and modify as I paint.
I start with Three Tones at first and separate them so I’m always checking myself. After I lay the Three major Tones on my painting I can refine it with Darker and Lighter Tones and even interchanging Hues as log as the Tones are alike.