Many special effects require only a toothpick or very small paintbrush to pull off. For example, marbling nails require pulling the small paintbrush through a speck of darker polish to give it a finely veined effect like the natural stone.When gluing on crystals, it’s important to use tweezers. With tweezers, you can drop the crystals in dots of nail glue but do it very carefully. With practice, you’ll be able to place crystals like a professional.