Been going to a workshop with Millie Gosch, she has been using some Peggy Kroll-Roberts inspired techniques with us. Each small study was painted in 25 or less brush strokes. The largest piece is 6"x8", the others are 5"x7".
We have been doing a great deal of painting with black, white and gray and then working accurately mixed color/ values on top of that. It has been great. It really makes you check your colors.
Basically, it teaches you to design the painting well in gray and then stick to that value plan.