what i do to lvl up Pokemon is give experience share to a Pokemon tht i want to level up and battle the whole elite four over and over and over again.if u cant access the elite four i would use vs seeker alot and battle.(if its possible in Pokemon platinum)
Its the same either way.
It is a illness your Pokemon can rarely get. It starts by Catching a wild Pokemon with it. It helps your Pokemon level up faster. It also slightly lowers the stat gain.
level them up
It does not matter where you level it up.
Level it up to level 40
Level up at level 28
level him up to level 30
It elevates your Pokemon up one level.
Get an Eevee and level it up in the Eterna Forest.
you train them
Train them............
if you want to level up your pokemon faster. give the pokemon you want to level up an exp share but it at the bottom of your pokemon list and battle and beat the elite4 in succession over and over until it is at the level you want it to be.