Kam i had the same deal.
I already had about 2 pages worth of Pokeballs and that little trickster made me use them all up.. the few times i cought him he had some useless Natures & i eventually caught a Timid one in a friggin net ball (go figure)
my strategy was Yawn with Munna.
come in with Axew and false swipe.
and there vuala..
now i have NOT one timer ball quick ball or even my ultra ball..
least i'm not the only one that caught it in a net ball...
I caught it on my 2nd ball
Sleep, then pokeball, then changed pokemon, then sleep again, then Leech Seed, then waiting waiting waiting and Work up work up work up, then just before death a Timer Ball !
Easy as pika pie ...