When I was a partner in a TT we did not put TP or any paper product in the black tank. We had a Walmart bag that hung on a stick-up hook down low and beside the toilet. All TP and other paper stuff went in the bag. If there is anything objectionable on the paper, just wrap it up in more clean paper. Take the bag to the trash every day and replace it with a clean one. There will not be any odor.
This was out of an abundance of caution, and a lesson learned when an uninformed person used HUGE WADS of TP.
Do that and use plenty of water. Wait until it's about 3/4 full to dump. No chemicals needed.