Hey guys, don't forget to take into account the relevant super-effective damage reducing berries, which in this case are Kasib Berries (Ghost Type) and Colbur Berries (Dark Type).
If you need to collect these berries in your game, these are wild encounter berries that you can find on route 20 (Kasib Berry) or on route 18 (Colbur Berry). They both grow on trees with purple berries on them.
What is a wild encounter berry? Sometimes, when you're doing a wild pokemon battle, trees will appear in the background. You can collect berries from those trees! Just have a pokemon that knows either twister, blizzard, or air cutter use that move against the opposing pokemon, and you'll find the berry at the end of the battle when you faint or catch the wild pokemon.
Need help finding a pokemon that knows one of those moves? One option is horsea, which learns twister at level 26. You can catch one at level 25 by using a good rod in Cyllage City or Ambrette Town. They have a 30% encounter rate, so you'll need to be a bit patient!
Also, blizzard is TM14, available for purchase for 70,000 poke-dollars in Anistar City Poke Mart.