Dog Heartworm Treatment

This is regarding the dog that was coughing last night with the question about benadryl. We did not give the benadryl and the dog slept the night, only coughing once early this morning.
Last night we gave him bread to help anything stuck go on down. He ate it eagerly and it did not change the coughing.
My daughter uses him as a demo dog for training (she is an apprentice). The location she trains is at a kennel so contagious illness is a possibility. He is consistently on heartworm meds and has been since he was a few months old.
To me the cough sounds like heart worm, but it seems to have come on too suddenly for that, plus he is on preventative.
He has no runny nose or other symptoms that seem to go with kennel cough. He is not acting sick.
The cough is less frequent this morning, but is still harsh sounding.
We will be taking him to the vet on Monday, but would like to help the cough now if we can.
Any thoughts?
He’ll be going to the vet; it does not seem to be an emergency.

She’s been scooting. I know that can be anal sacs needing drained. The vet did that a couple weeks ago, and said really they didn’t even need it.
The dog was still scooting when she got home. I also had a worm test done, and it came back negative. Sometimes she eats grass too, which I know can be a sign of stomach issues. She vomits once and a while too. I’m going to have another vet look at her, just wondered if anyone had any natural remedies or if it sounded like anything in particular. It cost me around $400 last time I had this checked (2 weeks ago) and it will be another month before I can afford that again. I’ve tried cleaning the area with vinegar which helps some.