For anyone who thinks they are not capable of learning to belch on command, the good news is that if you can swallow food or drink, the. You have what it takes to swallow air.
It requires lots of practice of course, gotta just keep trying until it clicks. I was taught how to swallow air. A fellow kid showed me how he did it, so I spent about half an hour at home trying to mimic what he did over and over until I got it. I was hooked since and started experimenting immediately to see how big I could belch if I swallowed more air.
You gotta be persistent, but anyone can learn how.
The inhale method is a different matter. It took me decades after learning to swallow air before I learned how to inhale. The one piece of advice that helped me most to finally get it was to bend forward at the waist as you inhale. Something about that position helped adjust my stomach to expand properly as the air sucked in. To say I was elated when I finally figured that out is an understatement, but even today if I don’t keep practicing the inhale, I have more difficulty triggering it consistently.
Gotta keep practicing…