Way I’m running it, what has to be overcome is fixed. I let them pick how, then make a single roll. Maybe 2 if it really feels appropriate. Then move on. If they chat up an NPC, I let them… until I think they are trying to either influence him or interrogate him… at which point, slap them with the test… every NPC they’ve met during GM phase who has a name is in as part of an obstacle or part of overcoming an obstacle.
In terms of rails, they’r on a swing arm attached to the rails.
In the player phase, I don’t even bother setting scenes… they do (within reason; I retain veto).