2-3 times a week. I have to stop typing in the dark and/or start proof reading!
For serious cases of poop butt like the one in the first post (from 2009) I would soak that nasty off her butt to prevent skin breakdown from the constant acidity and wet and treat her with Sulmet (use the directions on the bottle)followed by a few days of adding buttermilk to the flocks feed once a day. If the floor of you coop under the roost has lots of loose wet splats they treat the whole flock. You should see firmer poops by the third day at the latest.
As for the hen herself. Soak her bottom in a warm bath of mild soap and Epsom salts for a few minutes then gently roll her feathers between your fingers to loosen the gunk. Don't tug or pull the feathers. Change to water when it fowls and keep doing it until the water stays clear. Dry her or let her dry (indoors if it's cold) when this happened to our buff last fall I blow dried her on medium, she loved it. If her bottom is raw sooth it with A+D ointment. If it's stinky dab it with the cream women use for yeast infections. Check her skin in a few days and retreat with ointment if needed.
I know is sound hard but even if she fights you going in once you get her into the water she will calm right down. Mine fell asleep! When your at it you can oil her feet waddles and comb to clean them protect them from frost bite. I use vitamin E oil but cooking oil will work,
FYI for anyone who hasn't tried this yet: apple cider vinegar soak. It does wonders to clean gross underfluffies. Especially if one of your chooks gets fly strike (a real nightmare). ACV is truly lifesaving for flystrike.
