A cheap Pneumatic gun gun produces a lot more pressure than you can achieve with a pump gun.
https://www.harborfreight.com/air-grease-gun-219.html
Plus it leaves one hand free to hold the nozzle square on the zerk.
I also used the locking nozzles when working Heaving Equip years ago.
https://www.amazon.com/dp/B0752V7GLX...ams_ad_dp_ovrl