This is an idea I found on Youtube - originally for holding makeup brushes, but the same principle applies to art brushes.
When I finish using a paintbrush, I wash it and pat it dry. I reshape the bristles with my fingers, and insert it in the glass beads, which keeps the brushes separated. Brushes last longer when they are stored properly. And the glass beads are so darn pretty! Glass beads were purchased at Michael's floral department, the clear bowl was from a thrift store. Total cost $6.