As long as you've saved with the egg as an egg, then the IVs (PID, nature, etc.) are all already set.
(In fact the same is almost true a little earlier to a point, but that's irrelevant for this point.)
Just collect eggs (like a box of 30). Save. Hatch them all, noting which ones were flawless. Then reset, and go hatch those eggs in the desired location.
#1. Save with the eggs unhatched.
#2. Hatch them.
#3. Get them checked by the IV judge.
#4. If at least one of the eggs has your desired IV spread, reset your game, after which you can go to your desired hatching location and hatch the egg(s).
Edit: Ninja'd.
Thanks guys!