I like John Deere Corn Head Grease . I bought a grease gun just for corn head, unscrewed zerk fitting, replaced it with threaded cap . Remove check plug, pump some corn head in there, run machine a few minutes to melt grease. Check fluid level . Corn Head Grease is solid at room temperature, liqufies under shear load, turns solid when cool.
Bentonite Grease is also very good, hard to find .