I'd hold a jerky and let Magnus/Zoey nibble on them while I gently/slowly start brushing. I either start off from the tail end or the side. If they react to the brush like biting, I take the treat away. Let him/her relax a bit and offer the treat then start brushing again. I think talking to them helps. After all is done, they get rest of the treat.
It took few months with consistancy. They still don't love being groomed but they behave. Just be patient and I'm sure Buddy will come around. I used to "wrestle" with Magnus when I first started brushing him. Took me over an hour just to do a general brushing on him. Now, takes me maybe 15-20 min. But that's because I frisk him for ticks, wipe, detailed brush/comb, spritz with conditioner.
