Grooming a dog that hates being groomed
The problem is almost always noise and duration, not temperament. Here is the approach that works on dogs who have already decided against it.
Most dogs are not objecting to being groomed. They are objecting to a loud thing being held against them for twenty minutes by someone who has clearly decided this is happening.
Change those two variables and a surprising number of “impossible” dogs turn out to be fine.
Start with the tool switched on and nowhere near them
Put the clipper or vacuum on the floor, running, across the room. Let it be boring. Feed them near it. Do nothing else for a couple of days.
This feels like a waste of time and it is the single highest-value thing you can do. A dog that has already decided the noise means something bad is a much harder problem than a dog who has never had cause to care.
Two minutes, then stop
Not two minutes of grooming, two minutes total, then put it away while they are still calm. Stopping before they ask you to is what teaches them it always ends.
Most people do the opposite: push until the dog struggles, then stop. That teaches struggling works.
Back first, feet last
The back is the least defended part of a dog. Feet, face, tail and belly are the most. Work in that order across weeks, not within one session.
Nails are the hardest thing for most owners, and it is nearly always because you cannot see the quick and are guessing. A clipper with a light in the handle removes the guesswork, which removes the hesitation, which removes most of what the dog was reacting to.
When to stop trying
If your dog is genuinely frightened rather than merely unimpressed, panting, hiding, urinating, snapping, that is not a technique problem and pushing through it makes it permanent. A groomer who handles anxious dogs is worth the money, and so is a conversation with your vet.
Everything here is for the ordinary case: a dog who would simply rather not, and can be talked round.