Rolling the black walnut underfoot on a hard surface such as a paved driveway is the way I've illustrated. You can also distribute the unhusked walnut on a driveway that won't show stain while slowly rolling over them with an automobile.
Commercial huskers use a car tire rotating against a metal mesh. Some take a thick plywood board and drill a nut sized hole in it (from one to two inches in diameter) and smash the nut through using a hammer. The nut goes through and the husk remains behind. To keep the husk juices from splattering, a board or canvas scrap may be used to cover the nut before hammering.
After the husks are removed, the nuts should be stored in a dry place for at least two weeks to cure. Traditionally they are hung up in bags or baskets to provide better air circulation and prevent molds.