balance the hard with the soft
once you get a good feel for laogung breathing and can bring blood and qi to the palms,
get a stack of phone books and place it at a good height for a downward strike. when standing, ground/root/settle. raise palm 12-14 inches above the striking surface. make the palm heavy, take half a dozen breaths getting very still, settling, and making the palm heavy. then, "drop the heavy to the surface," as soon as "the heavy" leaves your palm, let go of it and let the palm fall with no muscular assistance whatsoever.
once the "thud" basically happens simultaneously ('the heavy' and your palm,) use a technique from yongquan breathing, ground and feel as if your entire body is the center, the laogung, and the contact of the palm coincides with the 'contact-strike' of the qi.
there's a ton of refinements one can do...
if you can feel potential at the lower dt, motivate it directed at the laogung and feel the wavecrest and analyze its analogue in the physical motion, the particulars of energyflow to the strike, but keep focus on the intent and not so much on the hard aspect of it...put your jin under a microscope.
there is also vibrating the palm before dropping...
one other important aspect is something master yang mentions in 8 brocades, the looking fiercely part - the niwan does this, a focusing of intent. the sharper and clearer the focus, the more focused the strike. every bit as important utilizing this aspect even when one is only doing the practice with intent.
once you feel you can express the qi well, a test you can try, get a large pail of water, place a soup bowl upside down at the bottom, place a square of tofu on top, and then have 4-5 inches of water over it....now work at it until you can shatter the tofu
Even in mildly complex systems, any outcome is the wrong thing to target, with the process being where the focus should be.