In the end I didn't get the vest. They are thousands of pounds and usually in a hospital for people who are lying in bed immobile. In US people seem to buy them privately for home use but not here.
By taking mucodyne liquid and using his acapella dad seems to have got on top of his mucous trouble. Sometimes he hardly has any in fact. We keep a close watch on how his lungs are and jump on any infections that crop up pretty quick. He gets IV piperacillin/tazobactam every 10 to 12 weeks plus whichever tablets will kill the bugs he sometimes gets in between. At the moment he's on doxycycline for strep.pueumoniae and seems to be clearing it up.
I hope you can find some good help for your dad and keep him as healthy as possible. It's not easy though and I wish you all the best,
Ps. I just noticed on your other post that you ARE in the US. In that case you probably could get a vibrating vest as they seemed to be very available there and I'd imagine bit more affordable than here in UK. It did look pretty good I must say. However if your dad is very frail and elderly it might be too vigorous for him. My dad is in his 80's now and very, very thin so I doubt he could wear one even if I did my hands on one. On a younger, more solid person it would be worth having a go. Good luck.