The WD-40 is OK but I prefer to use a carburetor-choke cleaner and wipe it down with one of the green Scotchbrite pads then paper towel. Depending on how dirty the rail is, it may take several applications. The imprortant idea here is to clean off the deposits and reduce the abrasion of the rail guide. Lubrication is best done sparingly, such as a silicone lubrication spray.