[anonymously]

https://www.youtube.com/watch?v=lR8bLPRkXkE Lot’s of good videos like this one over at YouTube. Just put dog teeth brushing in the search engine.
I use a medium brush and Petrodex (6.2 oz) toothpaste, Chewy. com carries it.
I pay particular attention to the back, sides, and try to get the inside back as well.

I would make a routine out of it, once or twice a day at the same time for at least 1-5 minutes. Take it slow at first till the dog gets used to it.