You will need:

2 cups plain flour
1 cup salt
2 tablespoons oil
2 cups cold water
2 teaspoons cream of tartare
few drops food colouring

heavy saucepan
Wooden spoon
Teaspoon
Measuring cup
Pastry board
Airtight container
Tablespoon

Method:
1. Mix all the ingredients together in saucepan
2. Cook the mixture over a medium heat, stirring constantly
3. When the mixture starts coming away from the sides, remove the saucepan from the heat
4. Allow to cool
5. Knead the dough on a lightly floured board to remove all lumps
6. When the dough is cold, store in airtight container

The dough will last half a term if stored in an airtight container (uncooked dough only lasts a week)
The models can be dried in a warm oven and later painted when cold.

Haven't made this so let me know how it goes!