Get the paint ready. A sturdy paper plate makes a great paint palette. Dab the circle sponge in the paint and really allow the sponge to soak up the paint. This may require more paint.
If you are working with a tank top onesie, simply tie the bows directly onto the straps and you are done. If working with a short-sleeve onesie, make the bow as you normally would. Then use a thread and needle to make a few stitches along the back center of the bow to the front of the onesie in various spots to secure.