Karl destroyed people on the low block, it wasn't until he was older and the entire league had retooled their line-ups with bigger stronger players to stop Karl (and others) that he evolved into a jump shooting threat.
But he did evolve and can teach the kids all aspects, would make him all the better coach. But back to the post. Teams would routinley send there center to guard Karl, and the PF to double, leaving Eaton alone on the 3pt line.
Karl was smart, he ran right to his spot on the block, never letting the defender have a chance to push him off the block. (Al posting up from 12 feet out makes me ill)
If the defender didn't seal Karl from the baseline quick enough Karl would step through with his right foot and seal the defender on his back and the pass would come baseline almost gaurenteeing a foul and most times a bucket.
If the the defender overplayed the baseline Karl pivoted on his right foot, sealed the defender by stepping his left foot into the lane and when he got the ball he could slam or running hook (Enes has demonstrated a similar running hook).
It was the early postioning and the smart footwork before the pass that made Karl great and it would be easy to teach to the kids. No need to teach them eloborate dream shakes, or the Al Jefferson pump and wait.