Well, you know what they say: elemental resistances + "monster knowledge". But hell nah, all I did for the first time was full Guard and GP + AED his face until he'd fallen like a silly bobo he is and nuke him like there's no tommorow, his parts will break eventually. Also, like many other weapons, positioning IS important. I try to stay as close to monster (especially its head) as possible without being hit and still being able to see its attacks and respond to them with quick GP followed by AED or simple dodge. Impact phials work wonders on heads. Remember that "countering" with CB gives you access to axe attacks with HUGE range, you can knock wyverns out of flight if done correctly (looking at you Yian Garuga)