Hi all, I am another one with mild bronchiectasis who could not produce a sputum sample with only dry cough. I was referred for chest (aka respiratory) therapy, and that is how I learned to start producing enough phlegm for culturing with the aerobika and huff coughing after 7% saline nebulizing. My first good samples showed Mac so I've been treated, so far without clearing.
I highly recommend the chest (or respiratory) therapy if you can access it. All best wishes to all on this invaluable site!