Lay raincoat on the floor spread open.
Avoid wrinkles where you are drawing.
Cut the toilet paper tube short so that you can draw with the marker inside of it.
Fill in the circle.
Space them up and repeat.
1, 2, ...
Try keeping a pattern like the 5 face on a dice.
You can first draw the outline and then fill in the circles.
Polka dots raincoat anybody!?
Ps. Avoid touching and smearing...