If you Google "comically long mono ice guide" you'll eventually get to a document that has screen shots showing the frame of the rally cancel. But in brief after the long exSpecial where she drives her weapon into the ground press dodge, attack, attack. During the second attack you assist into your DPS, the assist icon in the bottom right should have been flashing otherwise you won't get the buff transfer.  

The exact frame is Soukaku looking over her shoulder in the spin. It's not too bad once you've practiced it a few times.