We have a kitty that develops tartar and calculus like crazy. We brush her teeth, but we do not use toothpaste.
With her, we got lucky. She LOVED being brushed with a brush, and her favorite place to be brushed is on her cheeks. Because of the problem with her teeth, she loves having her gums massaged - so the transition to a small toothbrush that fits in her mouth was easy. She LOVES having her teeth brushed. The others don't - and we don't brush them. We do feed them treats once daily that help remove the tartar from their teeth.
...and we take the kitties for an annual dental. They remove the tartar build-up. Most vets don't recommend a dental annually until the kitties are older than like 5 or 6, I think.