I would go with a balance of both defense and offense. I would start by raising my Def./Sp. Def., then end the whole thing with strong offense moves like Surf, Earthquake, or Hyper Beam.
Another good thing to do is put them to sleep with Grass Whistle or Sing, or freeze them with Blizzard or Ice Beam.
Another good thing to do is put them to sleep with Grass Whistle or Sing, or freeze them with Blizzard or Ice Beam.