I had good luck mixing some nice bearing grease and 90 weight oil. Had to heat the two in a soup can to get it to blend together. Let it sit a couple of days and it didn't separate back into grease and oil. I made it runny enough that it flows veryyyyyyyy slloooowwwly. Almost like honey. Pumped it into the steering box with a grease syringe and never looked back. It flows unlike grease, but is too thick to run out of the seal.
-Jesse