Materials needed: string/wool, poster paints, paper
Dip a length of string/wool into some poster paint, keeping one end paint free. Take the string/wool and place it on your paper, either in a particular way or just as it natural wants to lie. Then give the clean end of the string/wool to the pupil and also them to pull it towards them, removing it from the paper. You can repeat this process using different colours, building up multiple layers.