My uncle Jon was a great guy. A statistician by trade, he was something of an introvert. His sense of humor had a hard, cynical edge that I always found refreshing, and the way he humbly expressed an altogether selfless nature through philanthropic activities remains an ongoing inspiration. So when my uncle 
You can see the end result above. The rest of this post is process documentation.
As you can see from this picture from my childhood, Jon had distinctive features, and was very good at looking skeptical. As my goal was not to immortalize his skepticism, but rather to commemorate his life for the family, I worked out a drawing from a picture where he was smiling and generally looking nice.
This was done on paper first, and then directly on the canvas, using colored pencil, charcoal, and marker. Next, it was time for the paint sketch, which I worked out in raw umber and burnt sienna.
For the brushy, impressionistic style of a work like this, I've found that eye placement and skull shape are the most important things to get right at this stage.
Once the portrait is sketched out, it is time to begin putting down some color.
For this work, I kept things simple. Just winsor yellow, cerulean blue, and cadmium red (along with titanium white and mars black to make greys)
The roughed-out portrait makes it clear where the work is heading. If a painting at this stage looks wrong, it is usually best just to start over. Fortunately, this one seemed to be heading in the right direction, so I kept at it.