I will answer with what I did - others may find a different routine that works better.
I used my bronchodilator first - either an inhaler or a neb, depending on how my underlying asthma was behaving. Then I used saline - followed by 5-10 minutes of airway clearance, depending on how much mucus was coming up. Finally, I would use my Tobramycin.
All using the same cup, rinsing between, although as someone else pointed out recently - it's all going the same place, so maybe the rinse isn't necessary.
Sue