Will swinging with softer shafts help find the feeling of PP3? The pressure is created by the hands being ahead and lagging the clubhead behind. With a really stiff shaft, do you need higher swing speed to get the same amount of felt pressure than you would with a senior shaft. A softer shaft bends more easily and in my head it should be easier to feel. There are training aids like the orange whip and some swinging with a chain that I would think helps finding the feeling.
The PBS is not something you have to play with all the time, but it's an aid that can help you find a feeling. You will of course practice with it, feeling the increased pressure, then trying to find a similar feeling without the PBS. Swinging a softer shaft now and then can help finding the feeling, at least I would think so. :)