After you beat the elite 4 you can battle wally at the end of victory road after you beat him exit then enter and his Pokemon will be stronger
To get a Pokemon level up quickly is to have a Pokemon hold exp. Share and then just battle a bunch of trainers or wild Pokemon.
Poochyena is a dark type of Pokemon. In Pokemon Emerald it will evolve if you raise it up to level 18.
you train them
You level a Pokemon up.
The easiest way to level up is to feed Pokemon Rare candies.
Victory road
Well you can't catch level 100 wild Pokemon in emerald, so get up and start training if you want a level 100
in elite 4.
There isn't really a specific time to how fast your Pokemon level up. The younger the Pokemon(smaller the level) the faster they level up. also battles the Pokemon is in give it more experience. so if you wanted to level up a oddish and you gave it exp. share it would get less experience than if it was the first in the party/ battled the enemy Pokemon itself. If you trade what you want to train to a friend and give the Pokemon a lucky egg it well level up really quickly, only a few hours to wait and it will be level 100 in no time.
train some electric Pokemon or just level up your Pokemon loads
cheat
There really isn't much you can do with it. You can level up some other mon to lvl100