I know Superpower breaks Ferrothorn, but you could get Power Whipped and Crawdaunt hates the stat drops. Plus a wall breaker should be able to switch in, so between Leech Seed, Leftovers, Iron Barbs, Protect, etc, Crawdaunt doesn't like Ferro. Whiscash can also KO Ferro with enough DD boosts using EQ, but neither is really an answer to Ferro. I've used Sap Sipper SD Sawsbuck in conjuction with Whiscash/Crawdaunt though. It is a pretty good partner wallbreaker and you don't have to leave those mons in a risky situation midgame.