Sometimes when things don't seem to be working, it's useful to go back to basics. Perhaps revisit https://bronchiectasis.com.au/physiotherapy and learn the theory behind airway clearance. Try different things to see what works. It takes lots of time and concentration.

For me learning to relax while exhaling gently was key. I found the stronger or harsher the exhale the worse. I wanted to get through the clearance as quickly as possible and I guess I sped things and there was more force, which was a hindrance. Once I took things down a notch things seem to move more freely. And it goes without saying lots of water and lately I've added brand name mucinex, which is helping to move the gunk. Hope this helpful.

PS - I find autogenic drainage and active cycle of breathing most effective