Prep: Acrylic craft paint in egg cartons, jars with brushes and water.
Directions: Put on old clothes. Go outside. Find rocks and paint them.
Rules: Paint only rocks. All painted rocks will forever live outside.
Success (in terms of hours): This was a very successful idea. 2+ hours.
Variation: Rock Faces. Paint eyes, ears, mouth, noses on separate rocks, then make mix-and-match faces with them.