This depends on what you need them to do specifically. If you’d simply looking for a pokémon capable of making precision cuts under strict guidance, the aipom family, kricketune, ninjask, the elemental monkeys, leavanny, the oshawott line, the pawniard family, sylveon, and scizor are all excellent choices. (Note: Contrary to popular belief, scyther is not recommended in such circumstances, due to its naturally aggressive nature. They may be better suited to gardening and topiary work, however.)
If you’d like a pokémon that can assist you with washing hair and fur, practically anything that can use Water Gun would be advisable, although the oshawott and panpour lines are both also capable of Cut to precise degrees.
Finally, if you’re looking for a pokémon that may offer some fashionable input, jynx, leavanny, and most fairy-types—particularly aromatisse and sylveon—quite frankly have the best tastes, objectively speaking.
Also, as a note, for assistance with dying pokémon fur or hair, never use a smeargle. Smeargle tend to take artistic liberties with their work, so they may do more harm than good. Instead, try jynx, as jynx are both careful and able to see color the way a human would.
Best of luck, anonymous!
The Pokédex According to Bill 