you can not get the feel of the trail hand action as I've described it
without actually doing it. I expect this is because the movement feels faster that ever experienced and this is likely because it is faster than the muscles in the trail arm can accomplish. Bertholy has some 'tricks' but none is quite the same as experiencing it until you do.
As the creator of this forum said when trying something I created before learning of Bertholy that was similar:
When I first replied to Peter about trying this swing, I told him I must be doing something wrong because I wasn't releasing. Like him, I was, but it was a totally different sensation than what I had previously experienced. And the video confirmed I was finally on the right track.
So if it's a totally different experience that had ever been experienced
then there is no way to experience it except to do it. I think this is the problem with the teaching of lots of pros; if you always had this experience then you are not in a position to explain how to get it or even in many cases to understand exactly what it is you're doing to experience it. Bertholy tells the story in his book of a top female golfer who had surgery on her trail arm and when getting back to golf suddenly realized how much her trail arm had been doing....to retain the club.
BTW - While I created the technique PhysEd described, I advise Bertholy instead.