*I've dont this* Even without writing in chalk, water painting on the chalkboard is amazing (read: clean) painting the kids love! Write letters in chalk and have child trace over with water. Just like wet/dry/try from HWOT! So easy
I loved doing this when I was a kid! Mom would let me "paint" the steps, sidewalk, etc. - what fun! Painting with real tools. Paint rollers, paint brushes and even a paint pan. But with water! Take it outside on the driveway and paint it!