it's not something you need to do regularly like with a dog. chickens do a good job of keeping themselves clean (most of the time
) i only give my birds baths before shows, occasionally after shows, if they're big ones just in case i brought home mites, and once, only once i did all of them when one rooster contracted CRD and after we put him down, we bleached the barn and chicken supplies and bathed every chicken to keep things clean, luckily all the others are very healthy now, thank goodness
i use either hand soap or i've found flea and tick dog or cat soap works wonders on parisite infestations as well as gets thier feathers clean and shiny. the one issue i've had is that one of my birds was actually allergic to it and her skin got really dry and started peeling! of course it was right before a big show
it didn't seem to hurt her otherwise, though, and she was the only one who reacted to it. in short, if you don't plan to show your birds, they can really keep clean pretty much on thier own, so baths aren't really that importent. not to mention the fact that most chickens HATE HATE HATE them!