I have been using white lithium grease in a can for my trailer ball. It seemed to work on the light utility trailer I have, which I use for short distances. I chose white lithium grease in a spray can, because I already have it, and it was lighter than the wheel bearing grease but did not run like silicone grease in a spray can, or WD-40.
Now, I would be towing a fully laden 6X10 enclosed trailer on a 1,000 mile-trip soon, and I want to make sure I am doing it right. So, what kind of grease do you use on your trailer?