See a pulmonologist.

They can advise you if respiratory therapy would be beneficial.

Thanks for the info!

OP, this article (which has quotes from doctors) may help with what to expect: https://www.thehealthy.com/addiction/smoking/health-improvements-stop-vaping/

I used to smoke cigarettes as a young adult. The beauty of a young body is that it is efficient at healing. Your lungs start to recover as soon as you stop inhaling toxic chemicals. I recall coughing up "stuff" for about a month or so after I quit. 20 years later, my lungs are healthy and they work perfectly. I have no lingering effects (that I'm aware of) from my 8 years of smoking. The challenge for your child will be not relapsing or starting a new vice.

Not interested in judgement here.

Wondering if anyone has experience with a kid who quit vaping and was able (or is working toward) cleaning up/rehabilitating, whatever, their lungs. I would guess that there are many 20 somethings who started vaping in high school at the height of the Juul trend who now want to better their health.

Any ideas appreciated. No need to hear about what an idiot my kid is for starting vaping in the first place. We know.