I think you can get an Exp. Share from Mr. Pokémon for the red scale and that boosts the exp. the holding Pokémon gains in battle if that's the only Pokémon that battles. Actually don't know this is post-league or not.
Otherwise pick up the phone numbers of trainers who hint that they might call to battle again, and they should crop up while you're training against wild Pokémon..
It takes a lot of patience but its worth it because after you defeat the Kimono girls you'll have to face Ho-Oh/Lugia and if you plan to catch them without the masterball you'll need pretty hgh levelled Pokémon to survive the blows. :)