is there any good way/place to grind exp?

[Nah]

Or is it like in Sun/Moon where level grinding sucks and your "best" option is E4 runs?

 

[HeroLinik]

You can SOS Chansey in Poni Plains. You'll encounter them from shaking bush encounters.

 

[BlazingFlame]

You can SOS Chansey in Poni Plains. You'll encounter them from shaking bush encounters.

This.

By the way, according to serebii, Blissey has a 5% chance holding Lucky Egg which means you can have more than 1 this time around.

 

[Alexander18]

I recommend Chansey S.O.S battles. Put a lucky egg on your pokemon and raise it's affection to two hearts.

Also you can have two five star Rare Kitchen's and be at least level 30 of Festival Plaza so you can quickly raise a pokemon to 100.

 

[Musical_Gamer]

Turn on the Roto Exp point power. That can help make the grinding session a little shorter.

 

[SquirSaur]

Grinding in Sun was a nightmare. I would like to see what they did in ORAS and have trainers be available to battle over and over, not just the E4

 

[SmartypantsGamingYT]

SOS Chansey battles on Poni Island, with the lucky egg(Which can be found right there, held by chansey).
Also denying evolution to a Pokemon increases exp rates and traded pokemons also get high exp.
Hope this helped!

 

[SquirSaur]

The game's already out, and we don't have that. :(

maybe in the next one????