This is the set I run and once the opposing teams Lampent is removed (worn down by ZHB, Golurk, Krow etc) it becomes fairly easy to clean with Drain Punch.
The two battles Ive played against hail played almost identically. 1. Wear down and kill Snover. 2. Wear down and kill Lampent. Ferroseed has been sacced at some point to take Blizzspam and set rocks. 3. Play around using Gastro and Cryo until I can get Krow in which then takes down a third pokemon. 4. Clean with Medicham/wallbreak with Golurk. The only trouble I've had with hail teams so far has been a Sub Rotom-F, but Medicham proved its awesomeness by tanking a Blizzard and one round of hail, recovering off damage with drain punch and clearing the remaining two pokes.