Practice man... I did so many pinch harmonics in the 80s that now I can get them out of acoustics. Sometimes when I'm playing stuff I used to play back then, I'll inadvertently pinch them out of muscle memory even when I don't want to.
Practice it is then. My Washburn seems to pinch alot better than my Strat, could this be because of the thicker strings? And about this screaming acoustic, that's something I'd be very interested to hear. Always been a fan of treating acoustics like electrics