Some reflux is bacterial/digestion related and some is structural.
If it is a low stomach acid thing, and the food is spending too much time in the stomach and fermenting before it gets down in the intestines, Betaine supplements can help. He can also get tested for SIBO (small intestine bacterial overgrowth) which can cause some reflux issues.
The most important thing for me was to drop anything with HFCS or other concentrated sources of fructose, like agave nectar immediately, even sauces (a bit of ketchup, sweet relish, or BBQ sauce, can get reflux rolling again).
Have him sleep propped up, to stop the acids from splashing up and irritating the esophagus quite so much.
Being overweight in the midsection (or pregnant, which I doubt he is) can cause the stomach acid to get pushed up too. As can having a weak stomach sphincter.