An excellent grease for bearings, widely available at Home Depot and other stores for around $4/tub, is Lubritech's "Marine Corrosion Control and Trailer Wheel Bearing Grease"; for a dollar or two extra, you can also pick up some "flux brushes" to apply the grease.

PS - Here's a not so cheap link that includes a photo of the tub: http://www.etrailer.com/p-l11404.htm