>>36596567Assuming USUM, you fly to Poni Meadow with only the pokes you want to level in your party. It helps if it has False Swipe. Give the pokemon you MOST want to gain XP a Lucky Egg to hold, aswell.
From where flying there deposits you, which is Poni Plains, go a small way south across the grass with the ambush until you're by the shaking shrubbery. Save your game. Now, AFTER saving your game, use a Roto Exp. Points. Then walk forward and trigger the shrubbery Ambush. If it's not chancy, soft reset, re-use the Roto XP, try again. Loading from save annihilates running roto bonus, so you have to do it after.
If it's chancy, False Swipe it down, use an Adrenaline Orb, SOS chain Chansey and Blissey forever with Lucky Egg & Roto Exp bonus. I level to 89 that way, then use the 9 level Rare Kitchen Buffet. Sometimes I'll have something that's at 79 from being in party with the others I'm leveling so I'll use that dish, too. Rest you can rare candy or normally level or whatever. Keep in mind winning Battle Agency always gives a Rare Candy, and you can get one daily on Melemele from a respawning spot on the ground.
The Lucky Egg you get after beating the Island Challenge by talking to Kukui in his house behind the Luvdisc Tank.
It really doesn't take very long and 1 rare kitchen is enough to do it.
PLEASE NOTE: Leveling from Rare Kitchen food DOES NOT evolve pokemon that cross the level they evolve at and DOES NOT ALLOW THEM TO LEARN MOVES they would learn at levels skipped OR reached exactly from eating the food there. You will have to use the Move Relearner or slow-level them to that level.