Use any good heat and water resistant grease.

Ordinary hardware store, farm supply store, Walmart, or auto store Lithium grease is as good as anything, and it's cheap.
Lithium grease was the issue grease for the M1 rifle and it works very well in auto pistol slide rails and on the barrel.

Lithium grease is a yellow-white color that doesn't make a mess like the black greases like Moly-Lithium.