Here's for those of you who need this info.
It's Best that you have a MachoBrace to do this.
PkRS (PokeRuss) has the same effect as MachoBrace, but it dosn't lower speed.
And it could be spread to all Pokemon in the party.
In order to get PkRS, you could be lucky and catch a wild Pokemon that's been infected. some say It's just as hard as finding a ShiningPokemon, but once you got it, you have a key to making your Pokemon sronger than normal.
Try asking your friends if they got it, and if they do, ask them could they Infect one of your Pokemon with it.
You can EV train your Pokemon without PkRS, but you'll finish quicker if you have
both (MachoBrace,& PkRS)
After you've done this, infect all the Pokemon you want to EV train.
Battle wild Pokemon with the one infected, and have the Pokemon you want to infect as your next Pokemon. Keep battling the wild Pokemon untill you infected your other Pokemon with PkRS.
Equip your Pokemon with MachoBrace, (MachoBrace, and PkRS together doubles all EV's).
Now that you've done this, you're ready to EV train.
Ruby, Saphire, & Emerald Versions
HP: Battle Marills (found near TheDayCareCenter)
Atk: Battle Shuppits, Poochyenas, And Mightyena (leftside of LilycoveCity)
Def: Battle Torkoals, and Kofings (in FieryPath)
SpAtk: Battle Spindas (found in Route 113) and pick up some ash too!
SpDef: Battle Tentacools, and Tentacrules (found almost everywere there is water)
Speed: Battle Zigzagoons, Linoones, Electrikes, and Manectrics (Found on Route 118)
Battle these for Many levels, untill EV's are maxed out.
You can only max out "2" different stats, so "only" battle those you need to increase the stats you need.
If you are not sure if you max out a stat or not, take your Pokemon to this woman standing next to the "EnergyGuru"in SlateportCity. She'll give your Pokemon an "EffortRibbon", if your EV's are maxed out, if not, she'll tell you to try harder. Then you do just that.
FireRed & LeafGreen Versions
Here are my EV training spots for FireRed & LeafGreen
HP: Dunsparce; Three Isle Port
Attack: Machop(1), Machoke(2);Mount Ember
Defense: Geodude(1), Graveler(2); Mount Ember
Sp.Attack: Gastly(1), Haunter(2); Poke'mon Tower
Sp.Defense: Tentacool (1), Tentacruel(2);(Most water spots)
Speed: Diglett (1), Dugtrio(2) Diglett's Cave
"Check it out!"