Unfortunately, what has seemed to happen to me the last few years is that I have had to scrap portraits due to the issue of my surface becoming too built up with paint to continue working on. This has yet again occurred :-( Whether it is light, choice of reference quality, changed eyesight, regression, or who knows, I have no idea. Instead of giving up, I decided to completely change my surface choice from stretched canvas as well as drop using the medium as a vehicle for acrylics and go back to water being the main vehicle.
I bought an Ampersand panel which is pre-prepared, 11"x14" and toned it in a medium warm stain of acrylic which I then wipe off slightly. I then drew the head and shoulders only this time, using charcoal pencil, which took a couple hours. My likeness seemed not quite 100% but I was pretty sure that my shapes and distances were fine so I dove into painting. I know a lot of the subtle shapes, contours and highlight/shadow shapes cannot be drawn in line easily but painting will mould them correctly.
I got fairly far in 2 sessions, about 2-3 hours long. I'm loving this surface so far! It turns out that a tiny bit of the medium has actually been a benefit with this surface, allowing me to drag and dry brush lighter tones over darker tones real well. But I am limiting use of it to only when it is specifically needed.
I have quite a ways to go yet but the tattoo on the neck will be the next thing I begin to tackle on this.