Tung oil is ok for items like furniture but I'm not sure I would use it for high wear areas like kitchen cabinets since you really can not overcoat it with a hard surface finish. The reason is it never dries. Your customers will have to rub on a new coat about every 3 months to keep it looking good. The good news is that they do not have to be heavy coats like you put on. Wipe on a light coat, go back and wipe off any excess. Be very careful with the rags that you or they use for this as they will spontaneously combust. The best way to get rid of the rags is put them in a gallon can about half filled with water.