@djf I used to have terrible problems with trapped air. I felt very uncomfortable, and I would force myself to burp frequently. For me there were a few things that I suspect lead to improvements. One major thing I credit with helping was eating enough and eating often enough and eating the right things that work for me.
Secondly, in my case, I found that consciously releasing or softening physical tension throughout the day, particularly under emotional or psychological stress was very helpful. As you probably know, stress of all kinds can interfere quite a lot with digestion quite dramatically both directly by altering digestion and indirectly by lowering metabolism. So modifying the physical response by releasing tension helped me tremendously. I noticed that I had a tendency to tense my jaw, neck, shoulders, chests, abdomen, hands, and feet – pretty much my whole body – in response to life. So I started to modify that habit, and I found it to be very helpful.
Thirdly, noticing my breathing habits throughout the day – not just as part of a practice – was very helpful. I noticed that I tended to hold my breath, breathe rapidly, use forceful exhalations, and breathe an excessively large volume of air much of the time. So instead of trying to do a dedicated practice, I found more benefit from noticing and relaxing my breathing habits throughout the day. For me releasing the habit of forceful exhales has been particularly beneficial in regard to digestion.
My digestion has improved dramatically. A few years ago I couldn’t eat more than 1000 calories in a day and I still experienced digestive discomfort, sometimes so extreme that I wouldn’t eat for a day or more at a time. Now I am frequently impressed by the dramatic improvements. I simply don’t have problems with eating or digestion.
So I cannot say for sure what your experiences will be, but in my case improvements in metabolic markers have corresponded to improvements in digestion. I believe that the things I have mentioned all work together synergistically.