Not quite the same, but we used to have to manage a padlock on our post office box through the winter. What worked best for us was to melt Vaseline in a tin, and submerge the whole lock in it, allow it to get most of the air bubbles out, and let it cool submerged. Then extract and clean the outside of the lock. Be careful of setting the melted Vaseline on fire!
This insured that there was lots of lube through the whole lock, and displaced any water that tried to get in. Might work for cave locks too.