Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you today. I do apologize that your question was not answered before. Different experts come online at various times; I just came online, read about your wee one’s situation, and wanted to help.
Now Saline Mist does not appear to be a brand itself (perhaps you have the generic), so you will need to list the ingredients. In regards ***** ***** Rhinaris drops, the can be used but it is preferable to use a product without Polyethylene Glycol. So, if you are struggling to find drops to use with your dog, you can just use OTC first aid eye wash or plain contact lens solution. The latter even comes in a bottle that can be used as one would with nasal drops. Of course, 2-3 drops per nostril per treatment.
Finally, just to comment on your chronic rhinitis issues, if the flush didn't cure this, then you may need to speak to the vet about culturing the bacterial agent present in the mucus with a view to possible systemic treatment. Or if that has already been done, then one may need to consider scoping of the nasal passage using a scope with a camera to see what is present +/- sample the tissue for analysis. This can be of great benefit in diagnosing chronic nasal issues due to fungal infections, tumors, and even related to immune mediated rhinitis issues.
Please take care,