I looked it up once and this is what i found... (p.s. this is the information i found not my actual words or experiance)
Instructions
Things You'll Need:
Three buckets or deep dish pans
Warm water
Mild soap, mild laundry detergent, or animal shampoo
Vinegar (white)
Plenty of old towels
1
Fill each bucket with warm water deep enough to cover the chicken' s body, but not its head.
2
Put a small amount of soap or shampoo in the first bucket, and approximately one-half cup of vinegar in the third bucket. The second bucket should contain just plain water.
3
Wash Cycle
Place the chicken in the first bucket with the soapy water. Gently slosh it up and down to loosen the dirt, pulling it off with your hands if necessary. You can also scrub the feet with a rag or small brush.
4
Rinse Cycle
Place the chicken in the plain rinse water and repeat the sloshing motion to remove the suds. Change the rinse water if it becomes too soapy or dirty.
5
Final Rinse
Place the chicken in the bucket with the vinegar. This will remove the soapy residue and make the feathers shine.
6
Wrap the chicken in a towel to dry it. You may need to use several towels. Keep the chicken on dry shavings or straw until it is completely dry. Dust and dirt will stick to wet feathers.
Tips & Warnings
Chickens don't particularly like baths, so you may need a helper to keep it from jumping out of the water.
Consider wearing long sleeves or protective cuffs; wet, angry chickens can scratch your arms.
Don't let the chicken' s head go underwater.
Never give a chicken a bath on a cold or chilly day.