Grey liners and pencils are commonly applied to the upper and lower lash lines. Some formulas are also suitable for the waterline, while eyebrow pencils are intended for shaping and filling brows. If you plan to use a pencil on the waterline, check the product label for waterline or ophthalmologist-approved wording.
Some grey eye products are marketed as hypoallergenic and ophthalmologist-tested, and a subset specifically note suitability for contact lens wearers or sensitive eyes. Availability of these formulations varies by brand and product.
Most product details recommend removing grey eyeliner with a makeup remover. Common options noted in listings include micellar water or other standard eye makeup removers; several products also state they are easily removed at home with makeup remover.