I'm having a tough time with it, and they just won't die, any suggestions?(such as a good poke defense, forgot what they're called.)
To give you an easier time on this fight, you can capture the Drowzee that appears a bit before this battle and use its Assist, as the Psychic Assist levitates the Pokémon in the air for a little while allowing for a much easier capture. Source: https://strategywiki.org/wiki/Pokémon_Ranger/Grimer_Outbreak