I just gave my silkie and my 4 coturnix quail a bath yesterday. I have to say that the quail did not appreciate it much, but they were decidedly stinky and we are keeping them in the house until I get my electric fence set up. A family of raccoons (aka satan's furry minions) got a hold of two of my birds through the wire, and it was not pretty. So they are staying in a large dog kennel in the house until I get my fence charger up.
I used a small tub and dawn dish soap. My silkie actually seemed to enjoy it, she snuggled down and got comfortable while I washed her feathers. Since it was pretty warm I just towel dried them and put them back in the cage, and they were fine. And might I add, I haven't seen many things funnier than a wet silkie! I wish I had gotten a picture!
My suggestions would be - get your supplies ready before hand, and get someone to help you just in case your birds don't appreciate your efforts. Have plenty of towels handy, have a cup to help you rinse, and a toothbrush or small pair of scissors for brushing/clipping out any stubborn matted dirt. Some people blow-dry their birds afterwards, but if it's warm and not windy I don't think it's completely necessary.
Good luck!