As to a bath, this is the advice I was given for white birds and found it works very nicely. I am sure there are other methods and tricks out there, too.
get four tubs of warm water.
First tub gets Trend with bleach alternative in it - enough to get the water a little sudsy- wash her well in this. Fill it so she is about half way in it- most chickens, I am told, love the warm and relax into it. My experience is that some do and some don't, so you may need an extra pair of hands for this.
Second tub gets a little white vinegar to rinse her and cut the soap- rinse really well.
Third tub gets a few drops of laundry bluing- this can be a bit hard to find. Kroger's carries it. Rinse really well in this also
Fourth tub gets a few drops of glycerine.
then wrap in a towel to get most of the moisture. You can use a hair dryer to dry, or put her in a warm place and by morning she will have worked it out herself.
