Hi all, first time poster here, and I'll be running a Dresden Files game in a couple of days (in a rather tweaked version of the World of Darkness setting). There are a couple of rules points I'm currently unsure on; I'd appreciate it if someone could clarify.

1) Devising Thaumaturgic rituals. The first step is to determine the spell's complexity and (if the complexity is more than the caster's Lore) do the preparation needed to reach that level. Does the caster need to do it just once for a given ritual, or every time they want to cast the spell? Neither way seems satisfactory to me. If the preparation is good for multiple castings, then a spell powered by e.g. human sacrifice only requires a single sacrifice, ever, because then the caster has completed the preparation already and doesn't need to repeat it. On the other hand, if the preparation has to be repeated every time, then how do spells like the Blood Rites entropy curse of Victor Sells' One Spoon Stab Exploding Heart Technique work? The writeups for both mention the casters taking hefty consequences on themselves to pay for them, but having done that, they can't take those consequences again. So how do they repeat the spell?

2) Grappling. Grappling is supposed to act as a block on all actions unless the GM rules on common-sense grounds that an action wouldn't be affected. Does this apply to dodging and other defence rolls? Again, I'm not sure which way to go here. On the one hand, allowing a grapple to leave someone defenceless seems overpowered. On the other hand, to have evading bullets be the one physical thing a grappled person can do seems rather odd.

And on a similar note, is it possible to specifically Block defence rolls, or to block Athletics and thereby prevent dodging?