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Most kennel cough dogs will run their course over 7-10 days. The most common at home anti-tussive that I have owners use is Robitussin DM. You can pick this up at a pharmacy and give it to your dogs.
The dose is 1/4 teaspoon for a small dog, 1/2 for a medium sized dog and 1 teaspoon for a large dog. You can give it every 8-12 hours, as needed.
If the signs worsen, then I would get a vet to prescribe some antibiotics. Most will resolve with at home care, though.
I hope this helps, let me know if you have any other questions.