To be honest, when I was frost spec'd I just had icy veins in my main cast (it doesn't trigger a GCD):

/cast icy veins
/cast frostbolt

For the water elemental, I had a separate hotkey to bring him up. Same for cold snap on fights where I needed him up again quick. Frost is nice because its SO low maintenance. That said, my arcane spec blows away the DPS of frost (for me at least). It does require more thought in rotation.