Easiest way to Ev train for competitive battling

Well the easiest way to ev train is Via horde battling.

And here are the locations for the hordes you need Also you will want to have a oddish with sweet scent to attract the hordes

Whismur
HP

Location: Rusturf Tunnel
Encounter Rate: 100%
Level: 5
EVs: 1 HP each
Attack

Shuppet
Location: Mt. Pyre (inside)
Encounter Rate: 100%
Level: 15
EVs: 1 Atk each

Sandshrew
Defense


Location: Route 111
Encounter Rate: 100%
Level: 11
EVs: 1 Def each
Note that Sweet Scent and Honey actually work in Sandstorm unlike in previous games!


Special Attack
Oddish
Location: Route 119
Encounter Rate: 100%
Level: 13
EVs: 1 SpA each
spinda
Location: Route 113
Encounter Rate: 95%
Level: 9
EVs: 1 SpA each

Special Defence
swablu
Location: Route 115
Encounter Rate: 100%
Level: 10
EVs: 1 SpD each

Speed
Location: Route 104 (North – Wingull, South – Taillow) and zigzagoon
Encounter Rate: 100% combined
Level: 2
EVs: 1 Spe each
Note: the route is divided into two parts by Petalburg Woods. Southern part of the route has Taillow hordes, Northern has Wingull hordes.