DS never seems to bring up/cough anything up. He's on duoneb and pulmozyme. And I think everyone has mucus in their lungs, nasal passages, etc., it's just that CFers tend to have really thick mucus. Before DS was put on pulmozyme, I could honestly say that he'd never ever had a runny nose. And the first time he used pulmozyme, I was amazed that his nose ran.
I DID notice that when the respiratory therapist at the clinic was trying to get him to bring up a sputum culture, he used HTS and DS started sounding really congested, the HTS and vest were loosening, bringing up a LOT of gunk. And it came time for DS to spit in the cup and he swallowed. Bleah!