One of my favorite practices, especially if I am out of the habit of painting and am having trouble getting going again, is to paint quick portrait sketches in my notebook. These are not precious, they are not meant to be shared or sold, and so I can avoid the intimidation that sometimes keeps me from diving in. I work from photo reference - anything with an interesting face and strong features and good light/shadow. Normally these are old black and white photos. I use a limited pallet of white, black, red and ochre, keeping things as simple as possible.
After a quick pencil sketch to get the features in the proper arrangement, I lay in the darks, below:
Then I block in the rest of the face roughly:
A quick background color to fill the page:
All of the above work takes about 15 minutes, and is done with the same brush, a number 8 filbert. I've been trying to get away from using Liquid, because it seems to make my brushwork too blotchy, and lately I have been trying to do the bulk of the painting with no medium at all.
Finally, I switch to a smaller filbert, a 3 or 4, and work the details, blend in color, etc.
Bertrand Russell
Another sketch, of Vincent Cassel:
