A little gun oil will do the trick. Just make sure it gets some lube...but I would stick to low viscosity oils rather than greases.
Gun butter isn't really recommended for moving things, like the slide, but for impact things at impact points, like maybe the face of the striker or lugs of a rifle. That's what they mean when they say, "It was designed to reduce the moment of inertia in moving parts and protection of high impact surfaces."