When DS was a year old, he developed a cough and a wheeze. I took him to the peds clinic, was told his lungs were clear. Probably "just a virus". When I mentioned the wheeze to his CF doctor he said "beat that cough/wheeze out of him". So we increased his CPT from 3 to 4 times a day. I also steamed up the bathroom while he had a bath to try to break up some of that stuff. When he had sinus infections, I asked his CF doctor about using a decongestant spray like afrin to get that stuff out and was also told that was a no-no.
We've always used saline spray, too although he HATES it. We used Simply Saline which is a compressed air spray -- over the counter. With regular saline sprays, I noticed we were getting a backwash affect from spraying it up his nose -- sometimes it'd act like a bulb syringe and suck all that nastiness back into the bottle. Bleah!