Also, if you dont know about PKRS, or Pokerus, here is its awesome effects when it comes to EV training:
A Pokemon that is infected by Pokerus, or has been cured of Pokerus, will earn double the EVs it normally would after a battle. This effect stacks with the boosts from Macho Brace and the Power Items. However, Pokerus does not double the EVs gained from Vitamins or Wings, which will be discussed later on.
It's recommended that you infect the Pokemon you want to EV train with Pokerus to save you a significant amount of time EV training.
The fastest EV training is done with a combination of Pokerus and a Power Item, earning EVs at this rate per battle:
(y + 4) * 2
where y is the amount of EVs you would earn alone.