Washable finger paint, paper, other items to paint, hose/water, towels to dry off
On a nice sunny day, let your kids strip down to a diaper or undies/swimsuit and let them fingerpaint outside. Have paper ready, but you can also let them paint on your kiddie table or let them paint themselves. My kids painted their whole bodies and all our kids toys outside. Then when we were done, they helped hose down all the toys and ran through the hose to rinse off. Just be sure to use washable paint!