This time, I worked with a thinner, more turped-down underlayer, made sure it was fully blended, and that the grey tones on the face were accurate. It felt a bit flat to me and half-way through I lifted up the canvas and realised that the brush-strokes were a bit careless, so I took it to the easel and this made a big difference.
Because I was working at a relatively small scale for me, my brush strokes were sometimes like dabs - and this felt neater. I mixed black and white on the palette to get the right tone, rather than on the canvas (which is what I often have done).