We drew overlapping shapes onto our 11x14 wet media paper. You can make a template out of cardboard or cardstock as the book suggests, but we had some PlayDo cutters that worked just fine.
The boys painted the shapes, except the overlapping areas, in primary colors. They then mixed their own secondary colors and painted the appropriate overlaps with them.
I found some $1 tablecloths at Walmart to cover our homeschool table--so much easier than newspaper, even if it is not very durable. I should be able to get a few uses out of each one.