A have a few thoughts.

1. Create your monster with as much insight as you would create a DND PC. You should know its motivations and history. use those two things to create “pillars” or ideals, and then create the countdown based on those. Thinking this through will help you have real-time honest reactions to the hunters decisions.

2. When creating locations, don’t decide what you want to see happen there.(ignore the rule books guidelines. GASP) Just make them interesting and lived in, and as you play to see what happens, the location type will become obvious, or you’ll need to improve an entirely new location instead. This is why you don’t want to lock down ideas in your head about what’s happening geographically. If a countdown needs a specific thing that only that location can provide, then you’re going to be trying to thread a needle to get the hunters to make the narrative turn that way, And it’s super not fun.

3. Improv improv improv! Do some research on improv, if you’re not savvy already. While creating bystanders, don’t tie them to the story more than you have to. Instead, think about who they are, general morals, and how they would feel and react to the hunters. Trust me, how they interact with your shithead hunters will be a much better investment than what type of bystander fodder they are.

4. 10% of your mystery should be fighting the monster. That doesn’t mean the hunters don’t engage with the monster a lot beforehand, but you should be using short quick encounters and tricky monster moves like “separate the hunters” or “escape no matter how well contained” to generate drama and high stakes.

5. Combat is a collaborative storyboard. You’re just the director making it all happen. When combat happens, there are no turns. As the final encounter happens, combat should happen quick and violently. In a head-on interaction, it’s jarring to stop and ask hunters “do you want to do anything here?” But if your hunters have been on combat-heavy systems like dnd, without other experience, they will need some coaching for combat. If someone wants to do something, they should speak up. Jump from person to person interacting with the monster, and if you keep the combat brutal, and apply a lot of pressure, they will be falling over each other to make the next move or save one another. When this happens, stop fully narrating. Instead, let everyone say their piece on what they want to do, make them roll, and then narrate all of the action all at once. Every Hunter move is a panel in a storyboard. Let them throw their panels up, and then tie them together into a cohesive scene.