So I deviated from my one layer, extact-color-match painting style and decided to build up a painting in layers. First I built up the blue and red hues under the skin to get warmer and cooler values (hopefully) with my skin tones.
Then I built up some of the highlights, like the nose and eyes, and went to work on the shadows with a little brown.
Then I added a peach/flesh tone over the top of the whole thing without testing it first. It was a gamble, especially since I didn’t thin out the paint at all (it was a mid-grade acrylic hue) but it turned out alright. After that I touched up the cheeks, nose and upper lip, put highlights in the hair, and raised up the collar and shoulders because I thought they were too low. This is how it turned out:
It didn’t end up being a 100% photo-realistic likeness of the subject, but it was pretty close. I’m pretty pleased overall.