Thanks. I didn't know Rid-X made an RV product. I'll keep it in mind when I'm parked for a while. And thanks for sharing your experience on other subjects too.
I normally use a capful of liquid laundry detergent after dumping. I mostly boondock so the "water and lots of it" suggestions won't work for me. I do dump some soapy wash water into the toilet- maybe a quart a day. I also drive my Class C quite a bit. I think frequent agitation is more important than chemicals or large amounts of water. I seldom notice more than a couple of... lumps going through the stinky slinky.
I dump at every FREE opportunity and when the tanks get close to full. I also rinse the tanks with a few gallons of water if available. If it's free, I don't complain about no rinse water.
I've also used liquid Calgon and don't think its any better or worse than liquid laundry detergent. It is really great as a laundry aid with very dirty clothes. I recommend it for that purpose. It is more expensive but certainly won't hurt your black tank.
I've been full time only for about 4 years but so far this has worked. I'm also a solo and that does makes a difference with water use. Recently I've been parked for longer (more than a week) periods and have become more interested in tank treatments.
Thanks to all for a useful discussion.