More specifically, is there an opportunity after the cascade trigger begins resolving in which you can activate abilities for mana that are not mana abilities in order to pay the additional cost?
No, there is not. You cast the revealed spell while the cascade trigger is resolving. Since the Shaman does not have a mana ability (since it targets, that makes it not a mana ability), you cannot activate it while the cascade trigger is resolving.
Private Mod Note
():
Rollback Post to RevisionRollBack
DCI Level 2 Judge
Scientists have calculated that the chance of anything so patently absurd actually existing are millions to one. But magicians have calculated that million-to-one chances crop up nine times out of ten.
No. They would have to tap the Shaman for mana before the Cascade trigger resolves. Casting the spell is part of the resolution of the Cascade trigger. There's no chance to use the ability once you know what the spell is.
Private Mod Note
():
Rollback Post to RevisionRollBack
Retrodrome!
Hoi, hoi, u embleer hrair
M'saion ulé hraka vair.
More specifically, is there an opportunity after the cascade trigger begins resolving in which you can activate abilities for mana that are not mana abilities in order to pay the additional cost?
Scientists have calculated that the chance of anything so patently absurd actually existing are millions to one. But magicians have calculated that million-to-one chances crop up nine times out of ten.
Hoi, hoi, u embleer hrair
M'saion ulé hraka vair.