@mustang1234 Colleen is correct - here is an interview with Dr. Madhav Chopra, a pulmonologist at Banner University in Tucson:
https://www.bannerhealth.com/healthcareblog/teach-me/should-i-use-mullein-leaf-to-clear-out-my-lungs
Mullein may help loosen mucus when used as a tea if you tolerate it. Water extraction of the active ingredients provides the safest method. Because mullein is not a regulated substance, producers are not required to disclose their extraction methods, this in depth article describes the many ways it can be done. https://pmc.ncbi.nlm.nih.gov/articles/PMC10046334/

The safest, that use minimal chemicals, are the most expensive. So if you decide to buy a tincture or drops, but the highest quality available.

Remember, with COPD, Asthma or Bronchiectasis, your lungs are already compromised, so doing anything potentially harmful can cause worsening symptoms.

PS When I need to help my lungs, I use Breath Easy tea from Traditional Medicinals. It tastes a lot better than mullein, which reminds me of dry grass.