This has been my routine lately:
Petzlife gel- 3x/week
Brushing with enzymatic toothpaste- 2x/week
It's honestly amazing how quickly the tarter comes off after using the Petzlife gel. It loosens everything up so that when you brush, 90% of it comes right off. I should have taken some before and after photos. I couldn't believe how well it works sometimes.
The bonus part of the gel is that it kills bad breath. I put a small tab of it on my index finger and wipe it on the roof of Kananga's mouth. His tongue coats his teeth and preps it for when he gets his teeth brushed. So far, he has very minimal tarter, if any at this point. I know my vet mentioned his teeth were in great shape last time he had his comprehensive exam. I bought the petzlife gel a few months ago and have not needed to purchase another container yet. It sure does last awhile, so don't get turned off by the high price tag.