PROFICIENCY FARM IN NIOH 2

You can temper proficiency gain on accessories.
Wooden Weapons gain you proficiency much faster but getting them is kind of a pain.
Don't forget to also equip any armor and weapons you need familiarity on.
Another perk of Golden Castle is that you can get Glue drops from the enemies there.

[Arisdex]

Also wooden weapons have +60% proficiency and on charms there are +10% proficiency each charm.
So +80% total.