For this activity we used some thin paint from few drops of food colouring mixed with water and an eye-dropper.
I gave Finn some watercolour paper although thick porous paper could also be used.
He experimented with colours running into others, and enjoyed the splattering effect the ink dropper made.
We used the same paints but used cotton tips to apply the paint. Cotton Tips made great painting implements for children, as they create fine lines, and are easy for them to control.
Allow the finished paintings to dry flat in the sun. Once dry you could ask your child if they would like to work into the paintings with a felt tip pen. They may find monsters and interesting shapes and patterns which they could work further with.