For about 6 years, I've been using Camper's Friend as the product works, has no smell and is easy to use. Prior to storing, I dump and flush tank as thoroughly as possible. Than and Camper's Friend along with a couple of gallons of water. In the winterization process, RV antifreeze gets added to the tank.
I agree that you can probably do fine without using any additives or using detergent, etc., black tanks will be stinky! When camping in hot weather, I want to use something to eliminate the smell as you do get a certain amount of fumes, especially if you flush while the ceiling fan is on. It should be mentioned that many folks are fans of the "Geo" method and you may want to research that topic.
