I used the chemicals/additives for a couple of seasons and honestly never noticed any difference at all. We settled on a short routine that works for us. After a camping stint...
-Dump as normal. Dump a couple gallons of water directly down the toilet at the end of draining the black tank and let that drain.
-Close everything up. No time wasted holding up everyone while 'rinsing' the black tank. Geez I hate waiting for that guy.
-Add one cup of borax down the toilet, wash another cup into the grey tank. Gallon or 2 of extra water into each tank and we're ready for the next trip. Driving allows the water/borax to wash around.
-If the black tank doesn't read empty when we leave for the next trip add a bucket of ice cubes on the drive out. If we're planning on an extended stay we'll dump on the way to get back the couple gallons of capacity.
That's it. Simple and quick.