Originally Posted by Fat SP458
Rock Smash on a Pokémon with a Modest nature (and without any EVs in Atk)? If it were Slaking, it might be good (and even then Brick Break would be better). But, a Politoed...
Also, your "problems" are either Water or Grass-type Pokémon. You should try something (read: Grass/Steel) which can cover most of them.
For Ferrethorn if he doesn't want to change any of his team Politoed can learn Focus Blast which does respectable damage against Ferrethorn (More so than Rock smash would.)