I like the SubSeedPunch Abomasnow set, lures out and kills the like of Tyranitar, Heatran, etc. I never used Froslass in OU though, but in UU I used a Substitute / Pain Split / Spikes / Blizzard set, although you can tweak that around a little. Personally I would make Hitmontop a bulky variant so it's easier to come in on Tyranitar, Excadrill, etc.