I have gotten the sound down, but I keep having these deep, and only deep but super short (<0.5 second) burps. I’ve been thinking about tightening my throat hole so it releases less air, but perhaps there’s something more to it?
Post a sound clip so that we know what it sounds like. It could be that you’re pushing too hard, I think it takes a decent amount of practice to apply the correct amount of pressure. Also how much air are you swallowing? That might make the biggest difference.