breed your HA Eevee with Modest Ditto and have the ditto hold an everstone. You will be guaranteed to get modest Eevees out of the eggs every time. From there just continue the breeding process till you get the 5 IVs perfect.
If you dont have a Modest Ditto, i can breed my Sylveon a bit till i get a Modest HA Eevee to trade you
If you dont have a Modest Ditto, i can breed my Sylveon a bit till i get a Modest HA Eevee to trade you