My new rabbit is really young and got poopy butt for a while. I had found out the previous owner was using soft wood shavings as litter, and once I changed him to care fresh litter that I use for my two year old holland lop, the poopy butt went away. It is REALLY hard to get the poop out I know, I ended up being very very careful about snipping out the poops that were hopelessly crusted. You are lucky you can actually trance him, what I would do is directly cut on the poop instead of focusing on the fur. sort of like manually grinding it with your scissors, and then rub between your fingers with vinegar. If you are still very scared, go to a bunny savvy vet and tell them to do it for you, or go to a grooming salon. If they refuse they obviously do not care about your bunny now or in the future so at least you would know not to go there. Can I ask what litter you use? And is it really a dietary issue or just cecals that your bun bun doesn’t manage to eat? My bunny is still a baby and only eats some of his cecals and then gets distracted. The poop sounds like cecals since it isn’t runny. Bunny diarrhea is unmistakable. Who is “they” that you refer to? a vet?