Waterline? Is that the lower inner rim of the lower eyelid?
A cheap but really good pencil is the Wet and Wild Kohl/Kajal pencil. (Kajal types are meant for inner rims. ) The best hygeine advice to prevent irritation is to use optomologist approved products, sharpen the product to get rid of gunk on the outside of the pencils, soften the point on your hand or wrist and line. Don't use inner rimming if you are a contact lens wearer.