The "tap" would be for a FTRB (failure to return to battery) that almost made it home, but not quite. This might be caused by recoil spring issues, magazine follower issues, or a too-tight extractor. A tap (more like a karate chop with the support hand, really) may be enough to drive the slide home and the round into chamber.
Obviously, this would be pointless with something like a stovepipe.
With regards to grip strength, there are plenty of tools on the market for that, some spring, some rubber.
For those who don't like buying gadgets, a couple other tricks work well.
1) Drive a nail or screw into a length of broomstick, perpendicular to the long axis of the stick. Tie one end of a line to the nail or screw, and the other end of the line to a relatively light weight of some kind. Roll the stick in your hands, to wind in the line and raise the weight. Good for grip and wrists/forearms.
2) Grab a decent quality bath towel. Toss it over a beam or upright of some kind (I like the pullup bars at the gym). Do pull-ups, or hangs if you can't do pull-ups, gripping the towel instead of a bar or bars.