Basically these are all suggestions. I don’t think there is one way to groom a bunny, Rex or not. Every bunny is different. Some will relax and enjoy being brushed, others combed, still others with damp hands running over them, etc, etc. And then some will allow you to only brush or manually groom certain parts of them and not allow you do so over their entirety. All different. You’ll have to learn what works best for you with your bunny. Sort of trial and error. As long as you are not forcing your bunny into a long grooming session via a method that it isn’t tolerant of or absolutely against, I don’t think you will cause GI stasis. I would also think it would be apparent real quick what your bunny will tolerate or not tolerate. Ours didn’t like combing and brushing. She would tentatively tolerate it if we sort of confused her with two people working on her. One person brushing and petting and the other person just petting so 3 hands petting and 1 hand brushing or combing. Of course ours was an Angora rabbit so her grooming needs were different in that she didn’t molt. At least not appreciably so.
But one person trying to brush or comb her. No way, uh-huh, not happening. She was disgusted and appalled at said endeavor.
And I suppose some common sense as to the brush or comb and how you use it. Obviously softer bristles over harder bristles. And more rounded bristles over sharp. Things of that nature. Because all bunnies do have sensitive skin.