After reading these posts I bought a grease buster. I've been trying to get grease into a fitting on my baler for 20 years. Each year I take the fitting out and soak the area in oil or PB blaster or equiv. It would never take grease.
I put ATF into the grease buster and it took about 15-20 minutes of tapping but it finally cleaned the gunk out and now takes grease.