EV training has nothing to do with Eggs; that's IVs you're thinking of. 31 is the max IV and if your hatchling has that, it's considered flawless in that category. Get all six (like a flawless Ditto I have) and you have a perfectly flawless Pokémon, the top percentile in its species, with only the nature having a factor in how well they do in a category from there. Hence why some find nature so important.
EV training is more like this. Hatch the Egg. Hand the baby an Exp. Share. Take a much stronger Pokémon in the party to battle the enemy that gives you the EVs (for instance, defeating a Herder yields two EVs for Attack). The Exp. Share holder is considered participating and gains the same EVs as the battler (the exception being the battler being maxed out already, in which case only the Exp. Share holder gets them).
You could literally take five babies and EV train all of them together for the same EV end results. Just hand out five Exp. Shares (either have willing traders or learn how to clone a Pokémon holding an item using Action Replay to generate all five). Just have a strong one handle Herdiers and run from everything else. Sooner or later, after 25 Herdiers, they all have 50 EV points and have gained some levels. You can then move on to Audinos to gain HP points (and more HP), or other enemies for similar results in Defence, Special Attack/Defence, and Speed.
B2/W2 also adds in EV-reducing berries at Join Avenue, something B/W doesn't have. Also handy for cloning to fully deplete the EVs in a selected stat for any Pokémon. Basically, if you've been quickly raising it on Audinos, some Pomeg Berries can be used to empty it, and thus start with a blank slate for EV training (this could reduce its HP slightly as well by removing the EVs; I have at times seen an HP adjustment of 1 between Audino battles, in fact, right after leveling up).