It is my understanding that you do not want to worm your chickens unless you know they have worms. Secondly you need to know what kind of worms which any vet can tell you from a stool sample. ( usually a very small fee). There are different treatments for each type of worms.
From what I understand alot of people use tearless baby shampoo to wash and aplle cider vinegar to rinse. Fill 3 tubs with warm water. wash in first tub rinse in second and rinse in third with a cup of vinegar.
It is very important that they do not get chilled. Some use low or air setting to blow dry and then keep inside a warm place over nite.
Hope that helps.