Well it was kinda hard for me but here a secret way to finish it ;o

Get ALOT OF items that can heal your belly and HP Better get Sitrus Berry
and if you got mobile scarf or a mobile IQ ability then use it
get alot of pokemons in your team and make sure they are leveled well and also link POWERFUL MOVES example : leer or growl then do a flame thrower = serious dmg to the enemy
and thats all :P also make all the team wear a mobile scarf or use the mobile IQ ability and thats all better yet if you can make your enemy sleep then it is a good thing BETTER EVEN YET get a ghost pokemon team they will be almost invisible :)