So, with that in mind I'm going to ask a really embarassing question. I'm hoping that people are going to answer it and then forget that I even asked it... 'Kay?

Okay, a mage has a Spell Pool. They can use their Spell Pool to increase the dice used for a Spellcasting test, but no more than the number of dice allocated from the Spellcasting skill. (Almost sounds like a separate pool at this point.) In using the Spell Pool to modify Drain Tests you also need to use one of your 'Spellcasting' skill dice, but this again limits the Spell Pool dice allowed to be used...
To recap at this point, if you had Sorcery of 5 (Willpower 5) to cast a spell but you wished to use 2 dice from it for your Drain Test, then you would cast the spell with an effective 'Sorcery' of (5-2) 3 modified by up to 3 dice from the Spell Pool. They could then make their Drain test using Willpower plus the 2 dice from their Spell Pool...
The same would obviously apply to Spell Defence. This is, in some ways, reminiscent of casting two spells at once, i.e. where you have to split your 'Sorcery' between the two spells...
But I'm relatively sure that is incorrect. I always seem to recall using the 'Pool' (in this case Spell Pool) as something that you dipped into when you wanted to. Yes it was moderated by your skill or attribute but otherwise it was a free-for-all. Thus for a Sorcery test for the above character they would be able to use up to 5 dice from the Spell Pool, but equally they would be able to use up to 5 dice (based from Willpower for me at the moment) for the Drain Test... Or, if they didn't use that then they would be able to use 5 dice from it for Spell Defence. The Pool obviously diminishes but your skill throughout doesn't...
If this latter paragraph is incorrect and you must divide your 'skill' between the various actions, then does this also occur with separate 'attacks' made in, say, melee and ranged combat. Say you're firing a SA pistol twice in a combat phase do you need to split the 'skill' between the two shots thereby limiting Combat Pool which can be used...? Again, this doesn't seem right. The skill should remain the same and the 'split attention' represented by the increased target number...
As I said, a really pathetically tedious question but please answer...

Anonymous... erm...
