Serving size: A quarter (near right). You don’t need to use half a bottle to reap its detangling, hydrating, shine-enhancing rewards. Coat hair from mid-shaft to ends, then comb through while in the shower to saturate strands evenly. Gently brushing through dry hair before you step into the tub can also help stave off tangles once you’re under the water, says Luis Alvarez, a stylist in Cleveland and a cofounder of the Aquage hair-care line.
Serving size: Two peas. Applied to wet hair, two drops will fight frizz sufficiently and keep hair sleek, says Rhys. (Since serums often have a heavy, somewhat oily texture, too much can make hair look greasy.) To tame flyaways throughout the day, rub one pea-size drop between your hands, then gently pat onto hair, working from the ends up.