The easiest way is to have a Wobbuffet. Since Wobbuffet has Shadow Tag, meaning the enemy cannot escape. Not only that, Psychic on a Psychic, not very effective. Wobbuffet should hold out for awhile.
On Paint's Discord. Still watching the site at least once a week. Go bother another admin or speak to me on Discord.
I used the dupe trick from Pokemon Emerald to duplicate my master ball 14 times (One for every available legendary.) Then traded over needless Pokemon holding master balls. Sure I now have 14 useless Pokemon, but it was well worth it. XD
Honestly the stragety ofchasing it down and throwing Quick Balls at it, Would take a long time
Just Get on at night, Have a wobbofett(missspelled) Have a few Timer , Dusk balls(i catch all my legendarys with dusk balls, Since im a nocturnal trainer) And ultra balls.
I didn't really care about catching it the first time I encountered so I threw a pokeball out of pure boredom.
And gues what...........................................I DIDN'T CATCH IT.XD