Here's what I did.
I put a Pokemon with Flame Body in my party. I would grab one egg at a time. From the day care, I would bike up to Castelia and back. Usually, the egg would hatch on the way back to the day care. I would grab another egg from the day care and repeat. I used this way to hatch a Jolly Shellder and a Jolly Sneasal, and I think I hatched about 30 eggs for each.
An easy way is to do the same thing, but put a rock or book on the forward and b buttons in the middle of the Gear Station. It will act as an infinite loop, so you can just sit back until the egg hatches. I also recommend filling your party with eggs first, because it's pretty far from the day care.
Hope I helped! Source: Experience