this is exactly how I do it:
infect the pokemon with pokerus and give it the item,lets say im looking for 252 special attack,im training a pikachu.
I give it an attack like thunderbolt which has decent pp,I will just battle psyducks,if a golduck I just flee. thunderbolt has 15 pp, I use all of them get to the pokemon center heal get back and battle 10 more psyducks,remove the item and battle one more.
now I have the 252 evs...im pretty sure I have done a good gob,but if there is anything wrong please let me know! ;]