I use a hypoallergenic puppy shampoo. I picked it up @ a pet store, rather cheap actually. Before that I had another brand(same thing though) that I got at Walmart, yay for $4 a bottle!
We use baby shampoo for most colored birds. But we use a bluing shampoo on the solid white birds, as well as mrs.wrights liquid bluing in their bath water. I hear some people use vinegar too, but I don't.
The only time I've bathed them was to show and we filled 3 containers with water. We mixed tail and mane shampoo in the first, white vinegar in the second and fabric softener in the third. They looked marvelous!