Well, if you cant corner em with mean look, damage them, as they keep it. Even better if you can freeze it. Since my starter knows ice fang it froze entei. Also if you have a pokemon that knows false swipe when its hp gets low use that. And then try and catch a pokemon and raise it to know mean look or block. Then just throw ultraballs at it. It may use roar to still flee though, so I dunno.