hot water, dry thoroughly and oil. Water never hurt these parts and water won't hurt shotgun parts.
I'd add that the water needs to be VERY hot, and that the gun has to be dried VERY thoroughly. We used hot water for the final cleaning of our M-1's at the conclusion of Basic Training. They were going from us to South Vietnam for our ARVN allies. With 200 guys all cleaning at once, the water temperature eventually dropped to not much more than warm. Some of the guys who were on the tail end of the cleaning process had to do a whole lot more later on.
