It feels weird to say but I hate them. I don't know if I Would describe them as painful, but they're definitely uncomfortable. It does not feel right in my chest or my throat. And I hate how irregular the rate at which I inhale/exhale air is when I try to do it slowly. And I can't breathe in/out for as long as I've been instructed to. Ok when I write all that out it kind of sounds like I have a medical problem. But to my knowledge my breathing is fine I passed the test with that thing doctors wear around their neck the stegosaur or whatevr
I've only ever tried breathing exercise stuff as something a counselor recommended to me for insomnia and anxiety issues where I got tachycardia or racing heart rate shit seemingly outta nowhere trying to fall asleep from CPTSD episodes, but they were mildly helpful in calming panic attacks and being calm enough to fall asleep.
I had a crunchy kinda new-agey relative recommend "fire breathing meditation" which from what I've gathered is pretty much just deep rhythmic breathing plus Zen type mindfulness and a quasi-throat singing guttural kind of exhale done in a pattern that was surprisingly kinda helpful. I've always had a really difficult time falling asleep but normally sleep pretty deeply once I do, so maybe that could help you if you're similar to me?
Idk, I was really skeptical of my relative for basically being "hippie bullshit" in general but that advice actually did help me. Still don't believe in homeopathy or healing crystals, but hey, sometimes kooky relatives have some useful tips, I dunno.