My doc told me if you try everything and nothing comes out, that usually means there is not enough there to come out. The trick is to not give up - at times, there may be a small amount.

For several days this week, I had no mucus come out, typically when healthy I see maybe a half teaspoon to teaspoon. Suddenly this morning, after my inhaler but before any clearance efforts, I started coughing, and brought up a lot (for me when healthy - more than an ounce of very thick, clear mucus.) It reminded me that with my house disrupted by remodeling, I was lax on my 7% saline nebs. I felt all cleared out after the coughing, and had no urge to cough after 90 minutes of dancing this afternoon, so I'll restart 7% saline tomorrow.
Sue