So when you say he's grinding teeth - he's grinding in anxiety or pain - not as a purr?
The reason I ask is Jack hates to be groomed too, but I have to because his fur is so course that it really just sticks to everything, and I worry about Rucy ingesting too much of this course hair, because she grooms him alot. (and he's twice her size so there is a lot of fur for her to groom)
I know what you mean about those soft bristle brushes - they aren't very affective with my bunnies. And the slickers bother Jack.
The HRS chapter I volunteer for introduced me to this comb. "HairBuster", Here is a picture of it, so you can search for it on the net. http://www.eurexint.com/ (I use the red one) I don't know anything about that particular online store, but at least this can help you with your own search if you decide to try the comb.
You use it by coming with the fur; you don't even really touch skin. You still have to be gentle when you get to a tangle. But usually what I do is brush, and follow with my hand - petting. So I pet, brush, pet, brush
If you can at least touch him, then use the wet hand method. Get a damp towel or damp hand cloth, a spray water & a water bottle. Spray your hands, rub your bunny, spray your hands thoroughly again and wipe your hands on the towel to get rid of a lot of the fur, and do the whole thing again.
WIth Jack, sometimes I just have to force the issue, but after about 5 -10 minutes, he calms down and actually begins to tolerate it, and lately he's been getting used to it. I would usually take him into the bathroom so he wouldn't constantly be trying to escape in his familiar territory. (of course, I would try the "force" issue as a last resort, especially since your bunny is so new to your household - needs to establish trust)
I'm lucky that Jack never holds any grudges, and even after being forced to be groomed he still approaches me to get attention.
Let us know how it goes.