We've only had Pepper a couple of weeks but we have been brushing his teeth every night since he came home. We use a fingertip brush that I put over my thumb and the Wahl brand doggy toothpaste - it smells like vanilla frosting!
I started by letting him lick and sniff/nip at the toothbrush to get him used to the feel in his mouth. I also put a bit of toothpaste on my finger and let him lick it off and he seemed to like it.
It's usually a joint effort where we wrap him in a Yorkie burrito (a great tip I got from YT!) and my husband sits with him on his lap and I brush his teeth. He still doesn't love it, but he tolerates it much better now.
We do it a little after dinner and play lots right before and right after. He also gets a carrot treat right after so he doesn't hate it as much. Lots and lots of praise while we brush and afterwards too! The whole process takes under 5 minutes now.
Hope that helps!