There are several ways to separate fats from sauces, gravies, etc. One way is to use a basting syringe. You may dip the syringe into the bottom liquid and squeeze the bulb to scoop the liquid up and into another vessel or you may dip the syringe into the fat itself and squeeze the bulb to extract the fat. A better way, perhaps, if there is time, is to refrigerate the liquid or fat in question. The fat will tend to solidify and it then may be easily lifted off or scooped off with a kitchen spoon.