How to brush a dog’s teeth that REALLY doesn’t like it and will bite😅

hey yall! i have a maltese/yorkie mix that’s around 16lbs and does those little alligator chomps whenever i try to brush his teeth. he’s always had teeth problems and i know he only bites bc his teeth hurt. even when my bf holds/restrains him he’s still chomping. he is very good at not doing what u want him to do. his teeth are getting bad again and even with the water additive they’re not improving and it’s becoming impossible to get a toothbrush in there and he needs that plaque off. he’s 14 and can’t go under anesthesia at his age so i really need to avoid dental work but it hurts so he won’t let me touch it 🙁

any advice for how to get his teeth brushed? any restraining methods would be great too. our vet has not had a lot of advice except for the water additive :/ hoping yall might know any methods that could work since he is so squirmy. thank u!!