Have your little one dab paint all over their wax paper. Splat it on nice and thick. The closer together your paint dots are, the better it is for blending the colours together in the next step.
Next, give them good-sized plastic lid. Our Gatorade lids were perfect, but the flat bottom of a glass or jar would work too.
Now, press and twist the lid into the paint, blending the dots together. Occasionally swipe the lid against a piece of paper to clean it off, to prevent the dots from becoming too “muddy”.