Clogged/Galled Grease Fittings

[Mundy]

After digging out as much crud from the removed zerk hole I would apply heat to the pin followed by penitrating oil. Get it nice and hot, not red but so it will make the first blast of oil smoke then keep spaying until its no longer smoking.
Let it set a while then repeat. Try to clean more gunk out of the zerk hole each time. Three or four rounds of this will soften very deep into the crud and it should start to take grease.

Good luck