I do occasionally. I have one Silkie hen in particular that gets a yucky bottom. Her name is Betty, but she's affectionately nicknamed Pig Pen, she's always dirty, not just a poopy butt. Mud in her beard, crest and foot feathers. Treats all over her (bless her heart, she's white once a year after she molts). She's got a really fluffy backside. I just bring her up to the hose (if its warm, if its cold I bring her inside) and wash her booty with some Dawn dish soap, then I smear some vegetable oil where the poop trail used to be to keep it from sticking to the feathers again.