I had some moly paste, something like 60% moly that I used to put on open steering gears. It's not quite as bad as grease at attracting dirt, and excellent for lube. I just cleaned it up real good and lubed it and wiped off the excess. I'd do it a couple times a year, and those gears were still in great shape when I got rid of the tractors. No matter what you do, it'll get dirty, so the only thing you can shoot for is some lube.