GamePress
For those who don't know, here is a great way to prepare for raids
In the pokebattler.com, they added this feature of putting the stat of your pokemons(up to 50) into a poke box, you can run the raid simulation and it will give you the ranking of your mons against every raid boss and its moveset. You can change the moveset, levels of your mons etc to see if they can perform better so you can decide if you need to TM or power up certain pokemons.