Back to the late 19th Century we went with a lesson on Pointilism...Suerat and Signac namely. I showed the kids examples of this French Impressionist approach, emphasizing atmosphere, color mixing and lots and lots of little brush strokes!
I had the kids create their own with q-tips and watercolor. This minimized the inherent want to swipe the brush and gave them a fun new utensil to try. While it seemed a bit exhaustive for some, most really embraced the limitation and did a great job.