Ah, soap brow! It's a simple technique used to create the illusion of thicker, fuller brows. To use it, start by choosing an eyeshadow color that matches your brows. Then, apply the shadow in short, quick strokes using a small, angled brush. This will help fill in sparse areas and create a natural-looking effect. You can also use a brow gel or pomade to set the color in place. With a little practice, you'll be able to create the perfect brows in no time!