Wash them in an old dish pan with warm water. Add the soap to the water before bathing them Then use another pan to rinse.I do this all the time for shows. I find the best thing to use is dish soap just the cheap 99cent soap is fine. Dont use Dawn as it dries out the feathers. Be sure they are partially dry before you put them outside so they dont chill USe a hair dryer on low to dry them. Oh yeah be care when washing them some chickens actually fall asleep in the pan and you have to hold their heads up. Unless you know the conditions of the flock you bought them from I would quarantine them to be sure they arent hiding any illnesses at least 4 weeks.