well it takes a hell lot of patience, u need to use the pokeradar to make the grass keep shaking and its good to hav repels with u cause trust me, youll need them, u know how u use the radr and u beat up a pkmn, so after when it goes bak to the screen another patch of grass shakes?
well u keep doing that till i think like u reach a high number of times u hav done it but sometimes the patches of grasstop shaking and that means the chain broke, so u need repels so that pokemon that arent from the shaking patches dont challenge u cause they break the chain, it takes super long but i hav now lots of shinies cause of it cause i spend hrs when i bored haha but trust me it isnt easy, it takes me like 3 hrs to get 1 but the chain breaks for me too also so i hav to start over and it kinda pisses ppl off