Acrylics have a great advantage painting portraits. I’ve noticed that the better I know a person the more difficulty I have getting a likeness. I noticed this when I was sketching portraits years ago and It was such a problem that I stopped doing them. I did try to paint a couple in oils, but had the same problem and it took longer because I couldn’t just erase them and trying to clean up a canvas is tedious at best.
Acrylics dry so quickly that painting over a mistake is a five minute job. Sfumato technique is a little challenging but moving features is easy and sandpaper works well as an eraser. I think this is the fifth or sixth iteration of various parts of this portrait. I tried freehand first but that didn’t work so I put an appropriate sized printout right on the painting surface. This works fairly well. I use dividers to transfer measurements from the printout to the painting. If an area isn’t working I start with the sandpaper then re-gesso the area and start again. I could use any colour of paint but the gesso has more of a sealing affect and it takes the next layer of paint well.
I typically use a printout to create images that I paint from. This works well if I need to isolate components or do a little editing. Colours however are muted, so if I’m comparing the printout to the painting I have to remember that the painting can and should have more vibrant colours.