They practiced using proper brush technique to paint squares neatly and smoothly, then with just a very small amount of paint left on their brush after each square, having painted most of the liquid carefully off onto the paper, they quickly dipped the brush into another color of the tray and painted again to create a mixed color. When they were finished, they practiced using a very small brush with watered down tempera to paint lines between the squares. After all of the painting was done, they drew a self portrait sleeping. They had lots of fun seeing some of the finished results hanging in the hallway.
I originally saw this lesson done by one of Mrs. Maheu's classes, thanks for the inspiration!