Creating aspects is, essentially, teamwork. I think what they're trying to describe is a quick way to work together in non-combat situations. There's less stress, so everyone creates an appropriate aspect and the person rolling the challenge tags all the aspects. In a non-combat situation, you don't usually have someone actively resisting. If you're trying to open a vault door, you have a set Difficulty, so it's easy to say, "here's the Difficulty, everyone can help." the door isn't going to resist the help.
Combat is exactly the same but/and you need appropriate justification and you have an active enemy resisting most of your maneuvers.
So, I'd say it depends on the action:
- everyone piles on a giant, trying to pin him to the ground: I'd say that everyone has to roll against the giants straight Might and the person with the main action can tag one of the aspects to initiate the grapple and every other additional maneuver helps improve the block. I could also see the giant resisting each individual maneuver.
- A guy is trying to attack: Each ally has to roll to do an appropriate maneuver, resisted by the opponent. "trip", "flank", "distract".
One ally uses rapport to "boost morale" That aspect might have a straight Difficulty since it's affecting allies and not enemies, although, /I could see letting the opponent defend against that with Intimidate.
- Someone is trying to run across an open field that's under gun fire. Allies all create "suppression fire" to add a block on attacks against the person running across. That might just be a set difficulty.
So, in most situations, I think the difficulty is the targets resistance roll. In some situations, it'll be a set difficulty but it won't always be 2 shifts lower than the main action.
Or, anyways, that's how I do it.
Haru uses a homebrew rule that you can use your action to automatically grant a +1 to an ally's action. (I think that's how he does it) Usually stuff like blocking movement etc.. I'm not sure if he uses it with straight attacks...
Edit: if you are doing maneuvers against the environment, maybe you can use the teamwork rules, since those have a set difficulty
Against the environment, the maneuver is
performed as a simple action against a fixed
difficulty set by the GM, which is usually very
context-dependent. For instance, knocking over
a table in a bar would probably be Average,
but finding cover in a barren desert could be
Great or more.
Although, I can see an enemy resisting some of these things. You knock over the table for cover, but the enemy is standing right there and pushes the table to the side as you do your action....
