Work out what he actually hates
Dogs rarely hate the idea of a brush; they hate something specific about the experience. Common culprits are a brush whose pins scratch skin through a thin coat, strokes that drag against tangles and pull, being cornered and held, or sessions that last twenty grinding minutes. Watch where he flinches: a dog who tolerates his back but snaps when the brush reaches the tail feathering is telling you about tangles and sensitive skin, not attitude. A dog who leaves the room at the sight of the brush has learned the whole event predicts discomfort. Your fix has to address his particular complaint, which is why observation comes before any new tool or technique.
Reset the association with food and brevity
Start over as if he had never been brushed. Bring out the brush at a relaxed moment, feed something excellent, and put the brush away without using it. Next session, do three or four light strokes on his least sensitive area — usually the chest or the middle of the back — treat, and stop while he is still comfortable. The discipline here is ending early: a session that finishes before he objects teaches him brushing is brief and rewarding, while pushing on to finish the whole coat re-teaches the old lesson in one evening. Most dogs turn a corner within a week or two of daily minute-long sessions, and the sessions can then stretch gradually as his tolerance genuinely grows.
Change the tools and the technique
Switch to the softest tool that still does the job on his coat: a grooming glove or soft bristle brush for short and fine coats, a slicker used with a feather-light touch for thicker ones, always stroking in the direction the hair grows and letting the brush glide rather than raking down to skin. Never attack a mat with a brush. Loosen knots with your fingers first, working a little conditioner into the tangle and teasing it apart from the ends inward; a mat that cannot be finger-picked without pulling should be clipped out carefully rather than fought with, because one painful rip can undo weeks of trust-building. Brush in layers on thick coats, lifting sections so you are not dragging the brush across the top while the undercoat beneath stays knotted.
Give him something better to do
A dog occupied with food is a dog not fixating on the brush. A lick mat spread with something he loves, stuck at his head height, keeps many dogs happily stationary through a session; a long-lasting chew works for dogs who prefer to gnaw. Position matters too: groom on a surface where he already relaxes, at a time of day when he is naturally mellow — after a walk and a meal, not when he is wound up and playful. Let him stand, sit or lie as he chooses and move with him rather than pinning him in place; a dog who is free to walk away and chooses to stay is genuinely consenting, and his tolerance will keep growing.
Daily minutes beat the weekly marathon
The endgame is a coat maintained in small doses: a minute or two a day keeps loose hair and early tangles from ever becoming the matted sections that require the long, pulling sessions he hates. It also keeps the positive association topped up, so brushing stays in the same mental category as treats rather than vet visits. Put it on the household rota like feeding or walking; on KinsLe Care Teams, a short daily brush can be assigned as a care duty for your dog and marked complete with a timestamp, so the coat gets its little-and-often attention even on busy days when a full grooming session would never happen.