Welcome to the forum Mike. You don't need to keep pumping until it comes out the caps. Just a little inside the spider and centrifugal force will do the work for you. It will work its way out to the ends of the spider when the uni is warm and turning. Its not good to pop the seals each time you grease them. They can stay dislodge and allow dust and grime to get in and destroy the uni-joint. I have used the GMB uni-joints on half shafts before. They came with an extended zerk fitting, but no plug to cap the uni-joint after greasing. I replaced all four zerk fittings with grub screws. Probably wouldn't effect vibrations, but one less source the better. That was my theory. Chas