I'm multiple sessions into playing/running Impulse Drive with a group, and we all love it.  We've run into difficulty with the Share Expertise move, particularly for the player with the Intellect playbook who frequently wants to use "Expert".

Here's an example: The group got into a secure building in search of information.  The group knows the information they seek is likely to be stored in a locked computer terminal, so once they get to the terminal, the Infiltrator declares he wants to Hack into the system to look for the information.  We decide the stakes are that a failed Hacking and Cracking roll would mean that they cannot get the information here, and they'll have to try to find the information somewhere else.  

The Intellect interrupts and says that he is an Expert in "programming, artificial intelligence, and cyberspace" and we all agree that his expertise should apply here.  He wants to help the Infiltrator gain Advantage to his roll to Hacking and Cracking.  We all think this makes sense, but we can't figure out how to run it mechanically.

"Expert" says he needs to make a move to enable it, then also mentions "you share your expertise with a crew member... for advantage" which the player took to mean he should be using the "Share Expertise" move as the trigger for Expert.  We all got into a discussion about how this should work, and none of us came to a satisfying mechanical approach.  In the end, I allowed him to roll+Calculating to give Advantage, but we agreed that this probably isn't the intended use.

My questions are: How does "Share Expertise" work?  How does "Expert" work?  What should we have done differently to explain this situation in a way that interacts with the moves more effectively?

great question, and I certainly understand where your groups confusion came from! There are a couple of paths I could see your group taking depending on the situation and the players'  intent.

First of all, your group's solution to the problem is totally valid! It's one that I would certainly have presented to the group. As players, your are the most important resources for finding a way forward in these edge cases - especially in the moment of play. Expert was definitely triggered, and I applaud your Intellect players instinct to enhance the Infiltrator's action, not supersede it.

The confusion comes from how some Moves are named, the criteria for more than one trigger being met simultaneously.  Expert of course, as you have mentioned, and Share Expertise - but the Intellect player's intent also points to Lean on Me being triggered. 

I usually approach these sorts of situations by looking at the player's intended outcome, fictionally and mechanically. Your group did this by having the discussion, and saying they wanted to give the Infiltrator Advantage. Expert clearly does that - if you can trigger a Move. Share Expertise interacting with Expert can do this. The Intellect shares what they know about programming or this particular program as the resolution to the Share Expertise roll, then as Expert interacts with it, they choose to give the Infiltrator Advantage.

The other way I could see this playing out is with Lean On Me. If the Intellect player really wants to play on the angle of helping the Intellect & their relationship as the point of tension, the Intellect could roll Lean On Me, with the intent to use it to help the Infiltrator - probably by giving them Advantage. Expert would influence this roll by allowing the Intellect to choose 1 more or less option from the list in Lean On Me.

Thank you so much!  This is exactly what I needed to understand.  I had suggested using Lean On Me during the discussion at the table, but I think the player was attached to the idea of using +Calculating because it gave him better odds and fit his character concept.  However, I hadn't considered the ability to choose 1 more or less option in the Lean On Me result, and I think pitching that to him would have helped.

The group at large is still a bit confused about Share Expertise as a general move.  Can you give an example where a player might want to use it?  Is it always used to establish something new in the fiction?  My players have been using Scope It Out to ask me questions that I haven't already answered, but Share Expertise says the player should ask me a question.  Since Scope It Out and Share Expertise are both roll+Calculating and both about asking questions, when should each apply?