After 34 pages all I can say is – amazing work, people. It’s been inspiring (by seeing how wonderful some of the finished results are!) and informative (to watch how people work in between stages).
I suppose I’m very late, but I thought I’d join in for something quick. I went for the first of the Sorolla head studies.
Painter, about 2,5-3 hours in total.
first three stages:

The first one isn’t very early on, because I forgot to save.
At any rate, I started by blocking in the main colours, trying to find the forms as I worked on them. This was done hastily, and I spent a lot of time in the next two steps correcting it, up to the point where I had to cut and paste his whole lower jaw, beard and all.

My palette – though I didn’t use all the colours. I mainly settled for ochres and umbers, and used the brighter colours as glazes so that it wouldn’t get too muddy. The blue wasn’t used at all – a simple grey worked where I thought I’d initially seen blue.
I found myself a lot of the time alternating between venetian red and raw umber (fifth on top row) a lot while working on the skin. I was quite at home with this, because I often use greens as shadows in my own skintones.
final image:

I liked the small red dot on the inner corner of his eye in the original – really makes a difference – so I copied it too. 