I saw this on The Artful Parent today and it was so fast and easy that we set it up right away. We painted with water on the chalkboard easel!
The boys love painting with water on the driveway, but today we're staying in. It's sunny but cold (and I'm a total baby about the cold), but more importantly: We're staying in because I'm PACKING FOR OUR TRIP TO DISNEY WORLD.
So water, paintbrushes, and an easel it is.