Here is the best grease gun I have ever used.
18V cordless grease gun Not for the faint of wallet. I have owned the Lincoln two-speed, but did not check to make sure it was all of the way in gear one time, and broke the gear box. Both are easy to load. Unscrew grease cylinder at the end closest to the pump, pull the plunger all of the way out, when you release it, it pushes the empty tube out, pull the plunger all of the way out again and lock it, install new tube after removing plastic cap, open end first, pull the pull tab off and screw cylinder back onto gun a couple of threads, release the plunger, pull the trigger until it starts pumping grease, tighten the cylinder. I use this procedure all of the time and never have air pocket problems.
Brian