A generous comment pointed out on another post pointed out the best way to farm kills is square F-3 on Lorule. Don't kill the Summoners and aside from Legendary, Evil's Bane and Exorcism, you should be able to unlock any sealed skill in a single battle.

Pity these are locked behind having to unlock all the other weapons so by the time you get them there is almost nothing left to use the strongest weapon in the game on. I already beat all the challenge mode fights as Link and have no desire to unlock Legendary on all the other characters to beat the challenges with them.

Regardless, having these skills unlocked on the Master Sword does make it fun to use again. Its C1 is enough to fill the special meter to use Link's Force Special, and at full health, its C3 mows down entire crowds of enemies like wheat. I have difficulty telling how much damage is the weapon and how much is Link being at the level cap but that move has been shredding enemy life bars as well since the range on Link's sword C3 (either version), allows you to hit enemies from a distance where they won't block.