Another voice to add to the chanting:
F3, F2 till low, Swiftcast, Flare, Convert, F2 (if you have a scholar and high enough piety, if not skip this), Flare, Ether of some sort, Flare if available.

Generally just

F3, F2 as much as you can (again as folks have said, 1 or 2 times usually), Flare, Transpose then get back to mashing the Fire III button

Its really inelegant and that down time waiting for the first mp tick before casting Fire III again goes against everything you've been taught as a caster dps (always be casting) but it really is the best way.