I also use Petzlife and CET toothpaste. Petzlife is a gel (or spray) that you put on their teeth and leave on for 1/2 hour. Afterwards I put on Petzlife I brush their teeth with CET toothpaste. I usually do this twice a week and it seems to keep the tartar off their teeth and leave them white. In addition, they get bully chew stick on a daily basis. I purchase my bully stick through one of the YT member (PM if want the contact info). I've tried Merrick bully stick before and they really smell. Whereas the one that I purchase from the YT member hardly smells at all.
BTW, I feed my furbabies dry kibble mixed with wet food. Good luck!