Hiya Kevin
When doing your inhaled meds (all of them), not only should you take the very deepest breath in that you can, but also hold it at fully expanded for as long as you can without letting any air escape from your lungs. This will force the air and meds inside your lung to equalise, which will hopefully push the air into the more dense part of your lungs (right lower lobe for you) and behind the trapped mucus. Hopefully after the treatments (leave it 15 mins or so) then do the huff/cough technique combined with acapella/flutter/vest to get that mucus out. I would also do physio/huff cough BEFORE you do your nebs, to clear the lungs as much as before inhaling the various medications.
This is what i did when i was first trialling Pulmozyme for a month and in that time managed to increase my FEV1 by 22%