When Jasper had kennel cough I gave him a vitamin C tablet every morning (I called my vet to confirm it was OK, I'd recommend doing the same if you decide to give Vit C) and a small dish of echinacea tea.

I gave tea in the evening one day, but that was a mistake that ended with a big puddle on the carpet at 3am!

My vet also said that sometimes giving the bordatella vaccine after a dog already has it can speed recovery time.