Welcome to BYC...sorry you're having troubles.
*****Thanks!! I guess it could be worse after thumbing through some of these threads.
Well, some kind of vegetable oil might help, that's what's often used when baby chicks get pasty butt....but, it may also gather dirt on an adult bird.
***My thought process as well for not trying it
You say her poops are normal and she's not sick.
Normal poops are usually solid enough not to stick to feathers.
Usually when poops build up it's because they are fairly 'loose'.
***They come out only slightly runnier that a completely solid poop. No parasites in it, no bad odor or colors.
Some questions:
Is she laying?
How old is she?
What and how exactly do you feed?
**** She lays 5 eggs a week, is 1.5 years old, and I order their food from Scratch and Peck. Organic no gmo with nutritional content by the textbook, plus they eat garden greens, a weekly yogurt, and free range so lots of bugs and field grass/weeds.
You say she's 'overweight'....what does that mean?
Is her abdomen and/or vent area swollen?
**** I just mean she's the same breed as the others but twice as heavy. Seems "thick." Nothing is swollen, vent is pink and normal. Just a big girl - I get Easter Eggers are the mutts of the world and she is probably mixed with a larger breed, but I swear she's the same height and width basically but like 4 lbs more.
I would examine her vent and abdomen close,
compare it by examining your other birds.
***Thanks for replying. She seems healthy, happy, and active and is actually my head hen. I don't mind washing her but I worry I won't be able to stay ahead of a future fly strike with chronic poop. This has been going on since the winter - my other girls don't have any issues.