[ElectivireRocks]

I think Glaceon will be the dominant anti-meta force.
Manual Hail isn't actually that terrible because it negates both sun and rain, making Vaporeon, Jolteon, Flareon and Leafeon less dangerous. It also makes Espeon and Umbreon's Morning Sun and Moonlight less effective. In other words, ALL eevolutions other than Glaceon are crippled by Hail.
Don't forget it also gets Snow Cloak so it could get lucky with some evasion hax.

Blizzard in hail is going to hurt everything except Vaporeon - even Flareon will take a massive chunk despite its special defense since its HP is so terrible.

Other than Eevee, Glaceon is the only one that gets a priority move in Ice Shard, and even though its attack sucks it could be used as a finisher against Jolteon and Leafeon, who both outspeed Glaceon.

Finally, Glaceon gets Mirror Coat and enough special bulk to use it effectively against Vaporeon, who would normally wall it all day.

As Flareon, arguably the worst of the bunch other than Eevee, is the only eevolution that has a type advantage against Glaceon, it can make full use of its actually decent bulk and act as a bulky attacker in this meta.

Specially bulky Wish/Curse/Ice Shard/Mirror Coat (if you can keep it away from Toxic and Flareon) and specially offensive Hail/Blizzard/Hyper Voice/HP Bug are probably its best options.