About a month ago I had a "lightbulb moment." I had been trying to help the kids keep the paints in the paint cups from getting mixed up with dirty brushes getting painted with, and then dipped back in the paint cup over and over again. It took me 2 1/2 years and a lot of paint to come up with this idea: THE MIXING BRUSH!
Here's how it works. I set out cups of tempera paint with one or two big brushes in each color. I put clean brushes in my pocket to use as "mixing brushes." I remind the class that they can use as many colors as they want to, but to not let the colors mix on their paper. That way, a brush with yellow paint doesn't pick up blue paint from the paper, and it doesn't turn the yellow paint cup green when it goes back in for another dip.
So, when the kids have put as much paint on their paper as they want, they ask for a mixing brush! This brush doesn't get dipped in paint, its usually a much smaller brush which makes it easy to tell the difference, and it's only job is to mix those colors together on the paper!
Now I should add that we paint almost every day at Honeybee, and there is almost always paint set up at the easel, and I don't give a lick about how the kids use that paint or if it gets mixed up a little bit. Other types of paints, like watercolors and tempera cakes, get water cups to rinse the brushes off between colors. So its really only when we use cups full of tempera at the art table together that we really rely on these mixing brushes!