Exhibit A:
Our focused practitioner (geomancer) attacks an major NPC who is giving orders to his goonies. Instead of inflicting stress he just wants to stop him to give out orders. Our geomancer has a bag of sand that he magically blows against the NPC. So he does a Maneuver to inflict an aspect like "Sand in the windpipe". How does this actually stop the NPC then.. should the player compel that Aspect (and giving the NPC a fate point) or what? Or is the NPC unable to command until he removes the manouver. And what's the difficulty in removing the aspect in this case, against the original channeling roll or something else?
Another option is to do a block with the sand, I guess, but maintaining the block takes his following action(s)?
If the aspect is established, it does exactly what it says, the NPC now has sand in his windpipe. However, that doesn't necessarily mean that it brings a bonus or penalty to each and every roll involving the NPC. When you create the aspect, you get a free invoke, called a tag. You can spend this tag like it is a fate point that you can only use on this aspect.
You can spend the tag (or after that fate points) to invoke the aspect. You can do that
1. either for a +2 bonus or a reroll when you are fighting the NPC and the aspect would be appropriate. Since sand in the windpipe should be pretty distracting, that should be almost always the case.
2. or you can go for an "invoke for effect" (YS99). This means, that you invoke the aspect either with your tag or with a fate point, and then specify an effect that is happening. For example, you could establish that he is unable to talk or even scream, as you say.
The difficulty to remove the aspect is equal to the shifts the maneuver was created with. If you do a 4 shift "sand in the windpipe" spell, then it requires a 4 shift action to get rid of it.
Exhibit B:
Our living dead reporter (yes) grapples a NPC goonie and uses his might to throw the goonie against the wall. Then he proceeds to ask "so how much damage does the NPC take from the throw..? ". "Err.. none", I answer with a straight face. As This was followed by disappointed looks, so I relented and gave the NPC an aspect "Spread eagled on the floor". This was probably not within the rules, but within the paradigm I think.
So now we have an NPC with "Spread eagled on the floor" aspect. How does this effect him? Is he on the floor until he removes the aspect? Or is it only taggable bonus for our PCs? Or both? And what's the difficulty in removing the aspect in this case, against the original grapple/throw or a standard "Get on your feet -roll"?
Well, what did he do, when he threw him against the wall? There are 3 actions you can do: attack, block, maneuver. A grapple is a type of block. If he keeps the grapple up, that's his action, and a block does not do any damage. However, when you do a grapple, you can chose to do 1 shift of damage (or more, if you have strength powers) as a supplemental action. That means that the strength of the grapple is reduced by 1 shift, but the character that is held in the grapple gets 1 shift of stress, which he can't defend against.
If, on the other hand, the grappler wants to inflict stress by throwing his target against the wall, that would be an attack action, and since he doesn't keep up his grapple, the target is automatically free now, but has to defend against the stress of the attack.
It's the same for a maneuver, the grapple ends, too. However, you can also put an aspect on the target as a supplemental action, if you like, just like the 1 shift of stress above.
If he doesn't do any of those actions, then throwing his target against the wall is just the way he describes him keeping the guy under control.
The NPC is effectively on the floor until he removes the aspect, yes. This should, of course, also mean that some actions are limited to him. Moving around, for example.