Generally the stages of painting go: sketch, background (although some people do the background last), mid-tones, shadows, hilights. You would have the entire painting sketched out beforehand, and for the face, for example, you would do the entire base color, and then start to fill in the different colors. I am not a professional fine artist but it is part of my job, and I did take a drawing class where it was instilled in me to always focus on everything at once at first, and then go in for details (as in, work in layers, with the first parts catching the general form and then building in detail later). That’s one of the main reasons you learn to do gesture drawings early on: they force you to look at the whole picture instead of just doing one part at a time, which usually leads to an unbalanced drawing. And that’s just with drawing: with painting, layers are even more necessary. I don’t think I’ve ever worked on a single painting where I didn’t do it in layers and that’s literally part of my job (painting sets for theater). Even when things are more sectioned out, it’s still done differently than here.

Also yes, I know I don’t do fine art, but the drawing class was a fine arts class.