1/4 cup shaving cream
1/4 glue
food coloring

Let the three year old squirt shaving cream into the measuring cup. Great sound effects. Then let him try to scoop it out of the measuring cup into the big bowl. Foam clings. Move onto the glue. You should move the glue from bottle to measuring cup (otherwise, your glue on the floor probability gets very high), but he can let it drip into the bowl. He stirs. Portion into three bowls. You do the food coloring. (You knew this right? The grown-up always does the food coloring.) With paint brushes and fingers, smear onto scrap paper and old egg cartons. Great texture. Great fun.