Turn exhaust fan on so that it blows in when flushing....
IF (that has been a few times in 30+ years) I get stink inside my RVs I locate source and FIX it
Couple times is was toilet floor flange (replaced it), sometimes toilet bowl seal (cleaned it or replaced it), one was a toilet that had 'overflow' that went directly to tank (plugged it off) and a couple AAVs that failed to close (Grey stinks also....replaced them) AND then there was having the exhaust fan on blowing OUT which would pull stink up when toilet was flushed.
But that few minutes was no worst then when someone 'went poop' and didn't linger
Besides poop just smells -well natural. Better than CHEMICAL POOP smell
Water provides a great odor barrier......that is why 'P' traps were designed to hold water, why residential toilets have built in 'P' traps.
Water is a 'solvent'---------natural
Water is heavy and will move boulders so and poop/TP will get carried out of holding tank if one allows level to be high enough
I just find 'chemicals' unnecessary... and after ALL the 'pros' for chemicals posted -----STILL find them unnecessary.