Brushing teeth some uses gauze at first,their are finger brushes,then long handled brushes, I have used a Oral Braum battery operated tooth brush on my old Papillon and now my Dachshund. You have to use pet tooth paste they also have Petz Life spray and a Gel also there is Tropic Clean Gel, Foam and a additive to put into the water the dogs drink. You should brush them everyday but at the very least three times a week. I have read using a tooth scaler is not good do to the fact it will leave little tiny scratches on the tooth enamel where bacteria can reside. Yes veterinarians and vet tech s uses a metal tooth scaler but they also polish the teeth after a cleaning which gets rid of the scratches in the enamel. Start them young less problems that way and good luck. Forgot some use Raw Turkey necks that is suppose to clean a dogs teeth all Buddy did with his Turkey neck is carry it around ? I brush his teeth about three times a week and give him Greenies and a antler.
Have you thought about giving some kind of raw bones, etc. to chew on either in addition to or instead of brushing. I've never brushed my current dogs' teet but we do feed mostly raw and give bones for teeth cleaning. They just had their annual visit and one is 9 and one is 5 and vet said their teeth look amazing. You can see Flirt's teeth below and because she chokes she gets fewer bones than anyone else.
I brush my Dobe's teeth after each meal. He is fed in the morning and evening. I floss between teeth that have a tight bite. In addition, I remove strands of hair that slip under the gum line. I did the same for my other Dobes. As a result, they have a full set of teeth their entire lives with no tartar buildup. By following this routine I have avoided putting them under anesthesia for professional cleanings as my vet says professional cleanings aren't necessary due to the great condition of their gums and teeth. I have my Dobe hold a solid rubber ball that is slightly smaller than a tennis ball. This keeps his mouth open so I can thoroughly brush each tooth surface. I move the ball as necessary to get to each tooth.