I have always used an EP grease from one of those specialist USA lubricating supply companies. Can't recall the name now but a tube cost over NZ$30 when a Castrol equivalent EP was about NZ$8. Used a small syringe to place a dab on the hinge pin/socket faces and the forend/action mating faces of my Miroku O/U shotgun after cleaning. Many years competition and many years bird shooting under wet and also often dusty conditions sees the gun as tight as the day it was bought new.