Toddlers will paint anything, anytime, anywhere. Young children seem to enjoy - brushes, rollers, hands, scrunchies, paper, utensils, ect...
When I recently filled the paint cups with clear water and a brush - the youngsters went to town painting the school buses, firetrucks, dump trucks and anything else they could reach.
Take the activity outside and they will paint the walls, the slide, the table, the fence and everything else in sight.
As the toddlers paint and paint, developmental skills in several learning domains; fine & gross motor, cognitive, self help, social emotional and language, are developed and strengthened.
The mess and clean up time - minimal, it's just H2O!