Another way to make it easier....short of genetics experiments to grow a third arm.....is to rig up one of your grease guns with the flexible rubber hose, and another one with the metal tube. Since the tube is threaded 1/8" pipe threads, you can use 1/8" pipe and make custom ones to fit your special needs. Doing industrial maintenance work in factories and mills all my life, I've rigged up some weird contraptions over the years. Once, to keep from carrying a ladder to grease a machine every morning, because you couldn't reach over the safety guards, I ended up with a U shaped bunch of pipe with elbows and such. Ususally have to braze a strap across the corners to keep it from unscrewing, but it works. Easier than toting a ladder every morning! Another machine had the seals out in the bearings on a 6 inch pillow block. This thing needed an entire tube of grease in each side every day. That's around 200 pumps per tube...yes I counted! It was out away from the buildings...no air, no electricity. Boss too cheap to buy me anything. So I took an old grease gun, pulled the plunger out of it, welded a 3/8 nut to the end of the gun, took a piece of all thread, put the piston on that, and ground the other end of the grease gun to a triangle. Then, I was able to use a cordless drill to run the grease out of that gun so fast it wasn't funny! Awkward, but fast! Just put your thinking cap on, and rig something up!