How to get bird poop off your doves feathers?

[FrostyWind]

Usually I could just knock the bird poop off their feathers but when it's like peanut butter, it's hard to remove every single piece that's stuck.
One dove sleeps below another and gets pooped on, even tho there's many more spaces to go cuddle up with each other, he prefers that spot to sleep at night. When he's bathing, nothing really comes off. Even when I bathe him, and brush off the poop with a toothbru6, some still stays stuck to his feathers on his back.
Is there something that could remove it all and have him looking like a normal ringneck dove?

 

[Quacking Pigeon]

You may need to pluck of trim the feather. But that may not be nice for the bird. Some of my pigeons get pooped on, but it eventually comes off after some time.