I really don't have a set formula for the progression of a painting.  Most of the time, I like to paint my foreground figures in first, and then paint in the background.  By using this method, I can make changes to the figures (like moving an arm or leg, or even a whole figure) without having to worry about what happens to the background.  However, on Between the Lines, I did extensive work on the composition of the painting, precisely setting all the figures where I wanted them before arriving at my final preliminary pencil sketch.
Due to the hundreds of spectators in the background — and wanting to get that part of the painting behind me—I decided to paint the foreground and background in first.  The foreground (grass) was painted solely by brush, while the background is painted primarily with an airbrush. At this point, I am ready to move on to the main figures in Between the Lines.
These are closeup views of portions of the background crowd.  I used acrylic paints with an airbrush to achieve the out-of-focus look.  I will go back over some of this acrylic airbrushing using oil glazes applied with a brush in the fine tuning process.
As you see in this picture, I have begun painting the foreground detail. As I move from back to front  in the painting, the detail will become sharper making the main action of the painting "in focus."
This close-up of the painting shows Lee Roy closing in on Jim Grisham of Oklahoma.
This will be our final update prior to the release of the print. I still have many hours of fine detail work left before it is complete.
[Between the Lines]