If you're one of the lucky ones with a black walnut tree in your yard, you need to get a plastic trash can to keep your brew in. No need to hull the nuts. The green part is going to produce the dye. Put the nuts in a nylon stocking, mesh onion bag, burlap sack or even an old pillow case. Tie with a strong cord, and tie this cord to the handle of the trash barrel. Cover with water and let soak till you have a nice brown dyebath. Maybe a week. Maybe less. Experiment with it. The bag should keep the dye from getting too messy, but if it still gets chunks of hull, strain out the pieces. Place the basket in the dye until color is as desired. You can use it over and over again. Add more hulls as needed. Add vinegar ( OR ammonia) to keep the mold down. Keep the can covered unless you have a bizarre sense of humor when it comes to the neighborhood raccoons- who are always looking for a swimming hole.