This is true only IF the location "has been hammered". Then, sure, you have to have better ears and superior machine to the prior hunters.
But I'm of the opinion that the "trick to finding old coins" is only 1% of the above "trick". Instead, the much bigger "trick" to finding old coins is: Location location location.
Why knock yourself out in hammered parks, trying to 'one-up' your competition, when you can find spots where no one's hit ? I've found seateds, gold coins, reales, etc.... that were only an inch deep, and could've been found with a harbor freight detector
metal detecto : A good place to "get your feet wet" and find some common silver & wheaties (to get your "practice" in), is: The yards of post WWII tract homes. You know, those urban sprawl neighborhoods that sprouted up in the late 1940s and early 1950s. That was a very prosperous time in the USA economy. Every kid had a few coins jingling in his pocket in those years, all the way through the 1950s and into the early 1960s. And those yards have probably never been hit (no hardcore guys are chasing common silver that requires door-knocking).