I'm only as far as the Elite Four, whom I've since mowed down and lost to Steven and have yet to try again.
I always have Talonflame or Larvesta in my party anyway. I stick the Poke'mon I want to breed in with the permanently resident Ditto, do a couple loops of Mauville on the Mach Bike, get the egg, then keep looping Mauville until it hatches.
Then I realize I didn't get the Poke'mon out of the day care, rinse and repeat, start Wonder Trading until I get something I don't already have.