My vet and I love nebulization coupled with injections. If you have more than a couple animals, it's probably worth it to pick up a little nebulizer and put together a chamber easily. I picked up a portable one for less than $50, although my husband gets stuff at cost since he works there part time. Your vet can give you the doses for it, show you how to use it if need be, and you should be good to go.
Sounds like you're doing the best you can. Kudos!