I don’t know about best, but I use grease on the bull gear of my Peerless just because it’s really awkward to get in there reliably with anything else. The bull gear is way in the back, and by the time I get my hand in with an oil can then try to see into the black insides to try to place it, well, it’s a shot in the dark to say the least. At least with the grease I know it stays put for a while and I don’t have to do it every single time I run the machine.
-frank