Wax resist is such a fun, immediate technique.
On good quality paper, make quick heart shapes with a white wax crayon or oil pastel.
Use quite watery watercolours to brush over them with a wide brush.
Kids love seeing the shapes magically appear.
We made a page of them and cut them into squares - great for making a quick Valentines Day card!
Visit my Valentine's Day page for lots more ideas, colouring sheets and free printables
http://www.theimaginationbox.com/valentines-day.html