RE: Emptying black and grey tanks
We camp in a seasonal site ( that has a full sewer) so our trailer never moves. I usually leave the gray water tank open and about once a month, I'll close it, fill it with water then dump it, just to give it a good flushing. I leave the black water tank closed and I add 8oz of the "blue stuff" in the tank. Whenever it's full, I dump it and give it a good rinsing (I make sure to close the gray water valve first) then add the blue stuff and a little water.
This seems to work well for me, I don't have any odor although, when I have to go #2, I usually take a stroll over to the shower house and use the facilities there, that helps considerably on the odor control too.
Cheers!