Wood coffee stirrer or toothpick
Glossy acrylic sealer (I used Liquitex Gloss Medium & Varnish)
Fill container with warm water. Drip nail polish into container. Pockets will form.
Quickly use stirrer or toothpick to expand the pockets of nail polish. Then dip your mug in a circular motion.
Let dry. Then add a glossy acrylic sealer with a sponge brush just over the design. You might need to add more layers of sealer, depending on your design. Be sure to let dry between applications.