Currently the is NO CURE for cystic fibrosis. Medical professionals vary in their opinions of which so-called natural remedies work for treating certain symptoms of the disease.
I am of the opinion that under no circumstance (except perhaps you've reached end-stage CF and simply want to pass painlessly from this world to the next) should a person with CF disregard a doctor's advice about his condition, nor should he forgo the basic medications that are effective in treating the symptoms.
Remember, CF is INCURABLE, but it is treatable, much more so than it used to be. I for one don't waste time chasing after untested natural remedies or comb the internet searching for herbal treatments and so forth. I prefer to go the tried and true route of following doctor's orders.