Draw a geometric shape or a picture on the paper and fold it in half (i.e. square, pumpkin, a person, butterfly, etc.). Let the child cut out the picture and open the paper.
Cut a piece of yarn (about 6-inch long). Put paint into the container and ask the child to dip one end of the yarn in the paint while holding on to the other end. Instruct the child to place the painted end of the yarn on one side of the paper, at the top. Fold the paper again and tell the child to pull the yarn out, from the bottom.
Open the folded paper, place the painted yarn at the top again, fold the paper, and pull the yarn out. Repeat these steps until the picture is painted.
You can use different colors and cut a piece of yarn for each color the child is using.