1. amulet coin/luck incense
2. chateau/e4 runs with generous spamming of Money power lvl 3.
3. Bargain Power lvl 3, purchase Vitamins, use them
4. Super train the rest of the way on lvl 3. With stats boosted by vitamins, the rest should be easy.
But yeah, sweet scent induced hordes work well too, provided you can teach that pokemon an area hitting attack that can hit and ko whatever you plan on running into.
Or turn exp share on and let the lead pokemon do all the work- the rest of the party will get all the same EV's too, so keep that in mind.