If you were like me, Smashmill is a hard pill to swallow when you don't know exactly how to use it.
Thankfully, a video can be seen in the link below:
[You must be registered and logged in to see this link.]The process is simple, really.
Start off with a Smash attack and charge Windmill right after the Smash icon disappears.
(you should know how to do this if you've worked out Ice-Counter)
Then, with Windmill charge, center the cursor UNDER your character and click like a madman when the enemy gets close.
(Note that the enemy may land a hit on you due to lag - have Mana Shield charged as a measure to protect yourself from the damage of an enemy attack)
Once the Windmill is completed, you'll be able to start the process again in order to inflict damage on the enemy while taking a minimum of damage from them. Works best on single aggro monsters, but can be useful for targeting the larger foes in a large enemy group. Just watch for multi-aggro.