How do you make Pokemon grow levels quicker if they level 30 and over other..

Fight the Pokemon in Victory Road or go to Artisan Cave in the Battle Frontier. Or you could fight the Gym Leaders again.

You see the red box near a name in your pokenav, that means that the other guy/gay wants to battle you again. Or level your Pokemon by battling the interview dudes.

Rare Candies or the Daycare.

Possibly you can focus on evening out your team? It sounds as if you're focusing on raising one or two or maybe three Pokemon, but at this point you should probably focus on evening out your team.
However you should know that sooner or later your level 30 and higher[s] will gain levels. And eventually you'll battle tougher trainers. It just takes patience. I know, I know. A lot of people hate that word. But to raise Pokemon, it really does takes a lot of patience.

Well the obvious answer is to train against higher level pokemon. The other answer is to use a cheat device to raise them quicker. But if this isn't going to work for you then you will just have to stick it out.

Go fight high Pokemon closer to the end of the game.

Easy,battle wild Pokemon,that are about 30+ level.

You can try training your pok�mon at the Elite Four, or even in the Victory Road Cave.

I would suggest you try battling them in the most recent routes that you have discovered or higher number routes.