It's easy to do this post-game, but manageable before hand.
The easiest way is to give Galarian Farfetch'd a Leek, (which it has a 50% chance of holding in the wild,) and teach it Leaf Blade via either TR or level-up at Level 55. If you don't have access to Leaf Blade, you can also use Focus Energy, which it also learns via TR, and a low power move.
From that point, encounter a wild Metapod that has high defenses and uses Harden, and just spam Leaf Blade. It shouldn't take more than 4 turns until you've made three critical hits, and your Farfetch'd will evolve.
Scope Lens works as well instead of Leek, and is a guaranteed item on Route 9.
Hope this helps! Please ask if you have more questions