Switched to the grease gun and my arms definitely don't miss the workout from packing bearings by hand. Honestly though I'm not sure the bearings noticed the difference, they don't exactly send me thank you cards. Figure if it's good enough for the pros it's good enough for my old truck.
Been running a grease gun on my trailer hubs since around then too and the bearings have held up fine. The one thing that matters is getting enough grease in there, so I pump until I see old stuff push out past the seal, then wipe it clean. Too little grease is way worse than the method you use. Just check them by hand at every oil change and you will know if something feels off.