This is an oil-based serum — how do I use it without it feeling greasy or interfering with my makeup?

Because this is an anhydrous (water-free) oil serum, application technique and timing matter. Apply a small amount — two to three drops is typically sufficient — and pat it gently onto skin rather than rubbing. Allow it to absorb fully for two to three minutes before applying anything on top. For morning use, letting it sit while you complete other steps (brushing teeth, etc.) gives it time to settle into the skin before moisturizer or makeup. Most users find it absorbs cleanly and does not interfere with products layered over it. If you have oily skin or find the texture too rich for daytime, using it as part of your evening routine only is a practical and effective approach.