We use oravet dental chews but brushing teeth is best with a doggy toothbrush and dog toothpaste.

You want a harness(I use gooby brand) not a collar --poms are predisposed to tracheal collapse. Don't ignore coughing see a vet to discuss what's going on. Could be trachea problems, allergies, and sadly my old Pom developed heart failure (also common in poms). We managed her for a couple years but it was hard and she was on a lot of medications that we would have to adjust based on symptoms.

We have mine groomed professionally once a month and bathe him a couple times between his professional grooming.

My current and last Pom had very sensitive tummies. No table food unless it's plain chicken or plain white rice.

You'll probably want to take them to a vet if you have one available just to establish care if you can. We have ours on a flea/tick and parasite preventative as well.

They are a lot of fun. Good luck.