have you tried a babys toothbrush? That may be softer, but I know what you mean. Mine fight it too, so bad where now I'm just using Cool & Clear Dental. You just put it in their water. I sell it on my website. it keeps their breath fresh and over time eats away tartar. So far so good!
Greens Treasured YorkshireTerriers | Michigan Yorkie Breeder, Yorkie Puppies for sale