Nope...I never clean my feeders. Mine are made out of wood, so no amount of scraping, hosing or scrubbing is going to get the dried residue of feed off those things. If you are adjusting your feed amounts properly, you won't have "leftovers" and all you'll see is a vague residue of the juice on the sides of the feeder. And, no, it shouldn't grow mold and such as it just dries out and their feeding efforts the next day will knock it off the sides of the feeder and into the daily ration.
Mold is more likely to grow in the absence of more healthy microbials~yeasts, etc., so your fears of mold and nasties are largely unfounded unless you are seriously mismanaging the fermented feed in some way, which is pretty hard to do.
I'll tell you a little funny about moldy feed....I had a feed can that had a few holes in the bottom of which I was unaware and rain had gotten in and soaked the bottom portion of my feed can. I started scooping into this feed at some point and noticed all the mold growth there. Took that feed out and tossed it in a pile in the woods and lined that trash can with a trash bag before storing more feed in it. Meanwhile my free ranging flock found that moldy feed, so I upturned a large rubber feed pan over it so they couldn't access it. I checked it later and noticed they had been scratching the feed out from under the sides of that pan and getting the feed anyway. I put a brick on the pan so it couldn't let the feed leak out from under. Some months later I happened to walk past that and noticed the pan had been shoved to one side and the chickens had still been scratching out that feed. I checked under the pan and there was just a little dab of feed left, so I just uncovered it and let it be.
None of those chickens took sick, died or even looked queasy after eating 1/3 a trash can of moldy layer mash and lived a long and healthy existence. It's clear to me that moldy feed fears are like stories of botulism in home canning....few and far between and always told as if someone knows someone who had this happen to them, but very few people actually are personal witness to such things.
