When I empty a fermenter,I wash out the heavy stuff with water & set it back on the fermenter stand. dump in 4TBSP of PBW & fill to near the top with water,stiring to dissolve. Lay the lid on & let it soak 5 days. Then a lightscrubbing with a bottle brush & rinse it out. I remove the spigot,seals,& lock nut & soak in a mug of PBW with the valve open. I use aquarium lift tube brushes inside them. Rise,soak in starsan a minute or two,then reassemble. A lot of nasties like to hide under the seal/lock nut area. So I remove & clean/saintize them & the mounting hole everytime.
On brewday,I sanitize the fermenter with starsan,no more smells. Most of them come from the spigot mounting area ime.