Collect objects with interesting surfaces (for example, cotton reels). Set out a printing workspace with: paint (ready-mixed variety, or powder colour mixed fairly thickly) in a tray with a thin sponge on top. The paint is soaked up into the sponge. It is important to allow pupils to practise the drill of putting the object onto the sponge pad and printing freely on a fairly large sheet of sugar paper.
Demonstrate the printing method for them. The aim at this stage is to promote a rhythm to the action and also to encourage a disciplined way of working. Once pupils have had sufficient practice at this (very young pupils will need several sessions), you can impose different limitations on the exercise. For instance: