Vitamins for up to the first 100 EVs (if applicable) and Super Training the rest of the way. A quick O-Power/Amulet Coin run of the Battle Chateau helps my medicine pocket stocked and the finer control over EVs with Super Training are a joy compared to how slow things used to be.
Horde Training is better in every way. Even on complex spreads, I use a combination of Horde Training and Traditional EV training.
For instance: To get 224 EV's into a Pokemon, I will.
1) Horde Train for 200 Points. 2) Find one of any Pokemon that yields the same stat and kill two (Or just Horde Train twice without the Power Items) 3) Find one Pokemon that yields that stat and just kill two of them.
Super training is cool, but I can always find Pokemon with the EV's that I need quicker than I can fire up that minigame, I mean, traditional EV training still exists.
3DS FC: 1134-8061-2200; SV 3273; IGN: Dano; List: http://tinyurl.com/meg2s5l Beartic, Piloswine, and Snorunt - My Friend Safari is Ice because I'm so cool.
Say you want to EV train in Attack. Take the Pokemon you want to EV, give it Pokerus and the Attack Power Item, and stick it on your team. Turn on the EXP Share.
Now take a pokemon with Sweet Scent and a multi-hit move. I like to use an Ursaring with Sweet Scent and Earthquake. Now take those two Pokemon and go to Route 19. Use Sweet Scent in the grass until you find a horde of Weepinbell. Kill them all with Earthquake.
Rinse and repeat, look up horde EVs online.
FC: 4725-8441-4984 IGN: Connor Normal Safari with Dunsparce, Audino, Eevee
Here's the steps I take if I wanted to max out any one given EV in a Pokémon's stat.
1: Buy 10 of the appropriate vitamin and use it on the Pokémon. HP Up for HP, Protein for Attack, and so on. Always use a level 3 Bargain O-Power before buying the vitamins.
2: Switch the bottom screen over to the Super Training screen (I normally have it on the PSS).
3: Withdraw Sweet, my Sweet Scent Illumise, from the PC and put her in front of the team, unless the Pokémon I'm training is high enough in level and possesses a suitable move for mowing down hordes in one turn, in which case they go to the front of the team instead (Sweet gets withdrawn in any case). Also withdraw a Pokémon with Pokérus and place it directly next to the Pokémon I'm EV training if it hasn't already contracted Pokérus.
4: Attach the appropriate power item to the Pokémon I'm EV training (Power Lens for Sp. Atk and so on)
5: Go to the appropriate location and use Sweet Scent to force horde encounters, and defeat the hordes with Sweet's Dazzling Gleam attack (or whatever move the Pokémon I'm EV training has that can handle whole hordes at once, if applicable). The hordes and locations I use are as follows;
*Plusle/Minun hordes on Route 5 also work for this, but due to their rarity, I only make use of them when EV training something in Attack or HP that I also intend to train in Speed.
6: Repeat step 5 until the Super Training screen will no longer give you the option of using a bag to increase that specific stat on that Pokémon.
It works very well for me. Those routes are never plagued by rain, and most of them are within easy skating distance of Camphrier Town. Yes, I know Zubat hordes are a little rare, but as far as I'm concerned, it's still quicker than waiting for the rain to let up so you can Sweet Scent for Murkrow hordes again. Trust me. I've Shiny hunted on those kinds of routes before with Sweet Scent. I know how long it can take. And I keep a small bag for each stat in Super Training specifically to test to see whether a Pokémon's maxed out its stats, plus a Reset Bag as a quick and easy way to tell exact EVs whenever necessary (save, use the Reset Bag, take note of the numbers it says it subtracts, and reset the game).
My fanfic: http://www.fanfiction.net/s/9247960/1/404-Error My Shiny Pokemon (not for trade): http://i.imgur.com/1utdapU.png