The role of Visual Effects Editor is both Technical and Creative.
Firstly the Sequence is edited by the Editor and the Director. Then the VFX turns this material over to the Visual Effects Company (in this case the Mill).
The Mill will provide Temp Animation which the Visual Effects Editor will Composite these temp effects into the Sequence.
Notes will be made and the Sequence will finally be completed.
This Short Video shows the process which can take up to 3 months