I've defined Brain Work as "the magic of magic. The power to alter leylines and Places of Power. The crystal clarity of thought. The way to read and control thoughts. Aligned with time." Now it's time to give the usual three spells as an example of what Brain Work can do.
Eye of the Storm: On a Great (+4) or better roll and spending a FATE point, the witch creates a temporary Place of Power around herself. The magic will dissipate at the end of the next scene, but until then, Face-Offs can happen here. The Place of Power is heavily tinged with the personality of the witch and yet not as powerful as a real Place of Power. There is no Leitmotiv, it has only one FATE point and the highest Asset of the witch becomes the only asset of the place at Fair (+2).
The Dragon's Path: On a Great (+4) or better roll, the witch may alter the Leitmotiv of a Place of Power for the rest of the scene without spending a FATE point. The witch accomplishes that by altering the flows of power around the place. A leyline was sometimes called a dragon's path. That's where the spell gets its name from.
Mood swing: When the witch succeeds with a Great (+4) or better roll, then she can lower an Asset of a character or Place of Power by 2 points and raise another Asset of the same character or place by 2 points for the rest of the scene.
Note: With Brain Work I am going a bit meta. But I think that's in keeping with the idea of this kind of magic.