You can give your pokemon a specific power bracer to train for particular ev...  
	Also I would recommend you to have a pokemon infected with pokerus which will double the rate of gaining evs...  
	My places are:
 
	attack:Peridot alleyways (pochyena and mightyena)
 
	Sp attack:Pyroas mountain (slugma and numel)
 
	Hp:Peridot alleyways (all the mons other than pochyena and mightyena)
 
	Def:Apophyll cave (geodude and graveler)
 
	Sp def: azurine lake (tentacool and tentacruel)
 
	Speed: Swoobat,woobat and noibat