The herbs Barberry and Oregon grape both contain alkaloids; berberine is one of these alkaloids which has the ability to destroy healthy gut flora as well as damage the intestinal lining. This is why I’ve never recommended either of these on the forum.
Yes, Oregon grape can help to clear the lungs, but there are safer ways to do this, plus I certainly wouldn’t want to use it during or even just after ridding the body of a Candida overgrowth considering the damage it does to the flora and intestinal lining.
Fenugreek seed can help to thin out mucous, and cayenne pepper when taken internally is able to stimulate the release of fluids into the lungs which keeps the phlegm thinned out. Then there are expectorants like horehound or osha that will help to expel the phlegm.