You're friendly neighborhood Tomohack here to drop some info if you are a lazy person trying to level up your max EV'd pokemon!
1. Drop your pokemon you want to level in the daycare,
2. Plug in your DS to charge,
3. Head to the Lumiose Monument,
4. Hop on your bike,
5. Shove a coin underneath the circle pad on your DS and forget about it!
6. Go eat some pizza, sleep, hang out with friends, whatever!
7. When you feel satisfied with your leveling, remove the dime and go collect your pokemans!
I've had this running all day and my shiny Gyarados went from level 29 to level 73. I'll have this running all night and by morning it should be level 100!
Note: You should probably raise your Pokemon in the daycare after maxing out EVs if you want a perfectly trained Pokemon. I suggest using EV calculators to find out which two skills you should train then playing the Super Training mini-game until you have maxed out the EVs you want.
Happy training everybody!