Draw circles on acetate with wax pencil. For smaller circles, use a compass. For larger circles, mark the center of the circle with a thumbtack. Then tie a string to the tack and tie a wax pencil tied to the other end of the string to keep the circle even in diameter. (Mistakes can be gently rubbed off the acetate with a dry cloth or paper towel.)
Cut into acetate over wax pencil circle with a matte knife. Always cut away from your hand, slowly and carefully.
Apply a thin, but even, coating of spray adhesive to the back of the cut circle stencil. When tacky, test on hidden area to be sure it will grip to wall.
Affix stencil to wall where desired. Make sure it is firmly attached to avoid bleeding of paint under stencil.
Using roller, apply thin layer of paint over the stencil, always working from the outside in toward the center of the circle.
Once paint is somewhat dry and at least tacky to the touch, remove acetate from wall and begin a fresh stencil. (Stencils will need to be disposed of after three or more uses.) Use your own judgment.
Paint should be completely dry before layering one color over another. Use a hairdryer or fan to speed up the drying process.