Back in 04 when we got our super glide we were told white lithium grease but that was a long time ago & it makes a mess. They do not use it now, so just call & find out what they want you to use today.
off subject but helpful
Now what I have to say is get a black or what color you like Tri-Fold canvas Tonneau Cover. I know you do not have grease, but it will still keep your hitch clean. Also no one can see what is in your bed when you are not pulling. When you pull just fold up out of the way. Get one made for your size bed with rubber on the bottom so you do not have to stick any thing on top your bed. I even have a 70 gal. fuel tank in front of my hitch under my cover. but that's another story.