Thor's teeth are awful. He had a teeth cleaning a few months ago and I can already see plaque forming again.
I used to wrap Thor up in a towel and have at him with the brush. Needless to say, he was not a fan. A few weeks ago, I took a page from
LilMissy's book and decided to go slower. Right now I just use the tip of my pinky and rub the toothpaste on his teeth and gums. Once he gets completely used to it, I plan to switch back to the brush. I can tell this is more effective because his breath immediately got much better. Every night I brush and floss my own teeth, and then I do Thor's.