I use a pneumatic grease gun with a needle fitting that replaces the regular fitting. Just press the needle into the ball on the zerk fitting and squeeze the trigger. You will have to pay attention to the settings on your compressor. Doesn't get any easier.
01 TJ, 34 Super Swaper 34x10.5 bias, Winch, locked, belly up, some armor, 4.0, 5spd