Chickens like to be clean. If you as their owner/manager keep their environment properly, they will keep themselves clean. I pick up my best flock pal, my black Ameraucana hen, Gypsy, who thinks she's a purse, I guess, judging from how much she loves to be carried around.
I bury my nose in her hackles and tell her she smells just like a dryer sheet. She truly does smell fresh and clean, unless she has been pooped on by someone else or has stepped in something along the way. They spend lots of time grooming themselves if you watch them for any length of time. If they step in something, they keep trying to get it off their foot-they don't like to be nasty, it's quite obvious to an outside observer.
If a flock is nasty and smelly, it's the flock manager's fault, IMO.

If a flock is nasty and smelly, it's the flock manager's fault, IMO.