I have started to add hair texture and the underpainting to the coat.
I am not content yet with the hair tone, but this is only the beginning. I don't paint each hair, but will add a few single fine hair strands on top of the texture and on the edges of the head when complete.
The background will need another layer too with some details in the shadows.

More tone added to the shadow part of the face along with minor tone changes to the mouth. I'm getting closer to the effect that I am trying to achieve but not there yet.
I shall begin to add the first layer of hair soon along with the mid-tone underpainting to the jacket.

Whilst I have added extra tone to the mouth and teeth, the shadow section of the face and the dark underpainting to sections of the coat, I was not feeling that the portrait itself was as close a resemblance as it should be.
I pinned it down to the shape of the cheek and chin and so, I adjusted the profile in this area. It will still need a little refinement when dry but I am much happier with the adjusted profile. The lower picture is the original and the upper one the adjusted one.
I think that part of the problem in seeing this is the fact that, although it is a portrait, it is not a conventional upright pose. Note to self: rotate the painting occasionally to view the image in a conventional upright pose.

 I have added some colour to the mouth which helps to convey the expression.
Darker flesh tones have been added over the pale underpainting which can be seen more in the lower photograph.
I am now beginning to enjoy this painting. I am always a little apprehensive when I start a new work which is probably why I am such a slow painter!
There are many tones and details to be added in the hair and face yet, but I may under-paint the coat/jacket in my next session which is the large area just below the mouth. This coat casts a shadow on the lower part of the face which will be an important part of the composition and will add dimension.

The shadow area is mostly blocked in. The colour is very neutral at the moment, and will need a number of layers to achieve the right tone.
The tones will need to suggest the perspective, as the top edge of the face will need to recede into the background.
As an artist, even with experience, I am always anxious that the painting is a success.

The underpainting to the hair is quite textured with crude brushstrokes, but this is intentional, as when the hair texture is added it will provide the variety of tones that occur in reality. Even areas of highlight over the top of a darker background will add 'depth' to the image.

 
Slow progress, as I have been busy with garden landscaping, but I have added more detail to the right eye. I shall add the underpainting to the hair area next as I work my way around the head.