Three witches are living in their cave, but a pair of lords are clashing outside and their armies are making so much noise. The witches decide to shut them up by casting a spell to turn the light drizzle into a deluge that will wash them all away.
The eldest sister has a Sorcery of B6, and will be the official caster. The middle sister has a Sorcery of B5, so her help will provide +2D. The youngest sister has a Sorcery of B4, so help will provide +1D. The cauldron in their cave is where they perform all their magic, and some of it has soaked in. It gives them one advantage die (assume they petitioned the GM for it).
They have plenty of time, since battles take so long, so they cast their spell, Weatherworker, carefully, resulting in +5D. However, this means their spell will require 120 actions (a minute or two). They also decide to cast the spell patiently, moving three dice from their casting pool to their pool to resist Tax. However, the loud noise from the battle is very distracting, so it increases the obstacle by one.
Once everything is tallied they will roll 12 open-ended dice against obstacle 6. This will be a routine test for the eldest sister and a difficult test for the two younger sisters.
Then they will all have to test to resist Tax, the eldest at Forte + 3 against obstacle 5, and the two younger at Forte + 3 against obstacle 4.
Is what is presented above correct?
This is less about making sure I have Sorcery understood and more about making sure I understand how various dice adding effect might apply. I just used a Sorcery example because by being more complex it had more things to work with.