I have played the Iron Guide (as I call GMing Ironsworn). :)
Totes_McGee says:
... For a strong hit: player advances narrative, within reason. ...
I would say: For any Move the Guide gives the players as much rope as the Guide wants. Just like in any RPG. This is that 'within reason' clause. Decide on a case by case basis how much narrative control the players have. The game system gives the players strong tools to do a lot themselves, but having a Guide transfers much of that control to the Guide, play it by ear.
Totes_McGee says:
... For weak hits and misses: GM takes control, imposes costs and setbacks. ...
Or adds some caveats and lets the player advance the narrative, or lets the player advance the narrative and adds a price, or whatever makes sense. The Guide is always 'in control', though, shaping the world around the players, so these 'costs' and 'setbacks' were part of the narrative already and the players should be including them in their narrative. The Guide provides guidance and proportion.
Totes_McGee says:
... GM also handles Fate Moves. ...
Look to the text of each Fate Move (I can not look at my books right now). Some may allow the players to handle them themselves, the Guide should provide guiance.
Totes_McGee says:
... The Ironsworn rules seem to want to cover every game type at once ...
They do try to cover all bases. But really they focus on Solo and Coop, you will find 'GM advice' lacking.
First, I should ask: What are your motivations? While Ironsworn bills itself as 'working for Solo, Coop, and Guided play' its rules really are focused on playing without the need for a Guide, when you play with a Guide many of the Moves fight with you a bit.
Having a Guide means that they are the Oracle, so players don't engage with that part of the rules (most of the book really:), unless the Guide calls on them to do so.
The Guide can use the Oracles as much or as little as they like (just like in any game, but with the added benefit of having pre-made tables that fit the theme (and are very well made)). They can also include the players in the Oracle process as much as they want (personally I 'always' roll in the open, so would do so with Oracles as well). It is tempting to try keep players engaged by having them roll on the Oracle tables, but that has no
mechanical effect, and just slows things down in PbP.
If you don't like the Oracle result, I recommend being open with the players and saying "It says '14: blah', but that does not make sense, how about we go with '15: blah' instead unless we prefer '13: eek!'" (It has been a while, I don't recall if Ironsworn includes the the 'rule' to 'use the option next to the result' if the dice result doesn't spark joy. I usually recommend looking one up and down, and even right and left in a multi-column table, when making Oracle rolls, because of this I don't like tools that roll and lookup Oracles for me and only show one result, I treat Oracles a 'area of the table' rather than a 'point'. But that's just me.) Oracles are a guide, feel free to ignore what they say if they don't fit.
Remember that, even in Solo play, you only roll when the answer is not already obvious, if you don't know what would happen. So, if the player and the table thinks a particular outcome is going to happen, and the Guide does not disagree, don't use the Moves. Though, be aware that many Moves drive the Progress mechanics, so don't skimp, it is always a balancing act. Many Moves won't get used, but this is always the case with Ironsworn, the style of game you are playing dictates which Moves are apropos (I have played a game where I never used any 'fight' moves, it was all social (and intrigue and magic)).
TheGenerator says:
... I think the role of the GM is different in Ironsworn compared to something like D&D. ...
Ironsworn is a big change from DnD, it might be a bridge too far if one is not already familiar with more story-focused games. It is a step on from
Powered by the Apocalypse (PbtA) and probably assumes some familiarity with PbtA.
TheGenerator says:
... Perhaps it's also possible to run Ironsworn with an existing dungeon in mind, but I'm honestly not sure how feasible it is. To me it seems that the mechanics get in the way of that idea. ...
As I don't tend to run existing dungeons, I can not comment too much, but I don't think that would be easy to do in a game designed around generating content on the fly (via random tables).
Totes_McGee says:
... Have you checked out Delve, the expansion? ...
I have read it, but never used it in play. As
TheGenerator says, it mainly adds more options specific to 'dungeons', but they are still random options, so would fight you if you used them with a set dungeon.
If you have a pre-made dungeon or adventure and want to run it with Ironsworn, only use the Ironsworn Moves or Oracles where the module does not already answer your questions. To me, this seems a sub-optimal use of both tools, I would rather go with a different tool in such a case.
Mythic Game Master Emulator (2e) would probably be my first choice (but that is about playing without a GM, so probably off-topic).
Totes_McGee says:
... I'm concerned players won't challenge themselves ...
As stated, your role as a Guide is that of a teacher. But you also control how much the players can get away with. In your scenario, I might let the players say what happens, if they 'break a nail' I would avoid chastising them and just say "yes, and..." and add on the real cost in addition to their broken nail. Incorporate the player's contributions of possible, but there is no need to turn the broken nail into the cause of the cost.
Don't imply to the players that their's is the only say, encourage them to add details and you finalise the outcome. The more they engage with the joy of negative outcomes, the less you will have to add. Teach them that these are not things to be avoided and weaseled out of, the costs are part of the fun. If they don't find 'failure' fun this might not be the sort of game for them?