Grit is a new item to Pokémon trainers. It comes in different sizes and is an important item that’s used to increase your Pokémon’s stats.
Players get Grit Dust, Grit Gravel, Grit Pebbles, and Grit Rocks. These different sizes of Grit increase a Pokémon’s Effort Level by varying points. Effort Levels increase your Pokémon’s stats further than what they already get from leveling up. The higher the level of Pokémon, the more effective the Grit is — and the bigger the Grit, the more it raises your Pokémon’s Effort Level.
Releasing multiple Pokémon at once is the fastest way to earn Grit on your journey, though there are a few other methods you can employ, just as defeating Alpha Pokémon, or trading it for better Grit.
Source: https://www.distractify.com/p/how-to-mass-release-pokemon-legends-arcues
