I managed to do a few more hours on this today. I must be getting older as I find I can only work 2 or 3 hours at a time on a large painting like this before I get too sore to do more. I think the next few paintings will be small enough to work flat on a desk again. :-)
I worked all over the painting darkening values and moulding the features. I am purposefully not adding more skin tones until I get the shading finished and then I'll put on the final colouring on the skin. I added another layer of colour on the shirt. I think I am going to leave this part fairly loose. I still need to correct the values however. The other thing I worked on was the hair. It will take many glazes of colour to build that up.
The photo doesn't show the subtle variations in skin tone that are there in real life. Still a lot more to do and the deadline approaches.