Years ago I used grease on the bottom of the barrel. When I pulled the barrel some time later the bottom of the barrel from the bore to about 10" back, had a thick layer of rust. After that I started using wax, plain old Johnson's paste wax, I had a large can on my bench.
Now I wax the exterior of my firearms, and use oil in the bore. No more rust. When I come in from hunting I take a hard cloth and rub the outsides down with fast strokes, no more fingerprints and no rust. Easy and less messy than oiling the outsides.