First, vibe check. Let the players shoot the shit a little more than usual out of game. While they do this, you do a little last minute brainstorming or note-taking/reworking.

Second, if you let them drive the convo, they will usually give you some clues when they finally get bored and start asking each other to calm down and start the game. Things like "I want to find out what so and so has to say about the mission we just got from who's his face!" Or "I want to kick that (minion of the bbeg)'s ass! Let's get moving!"

This tells you what your players want. Now you have some focus on what you need to spitball.

Now it's down to your improv skills. Yes-and helps a ton here. You ask what they do and it just works, or works with consequences. Ask them to roll some checks and if they roll high and it isn't stupid they succed and do the thing or get the info.

If they roll low something bad but not lethal happens. Minions show up, NPCs laugh at them, etc etc.

If you panic, ask them to roll a check and figure out what is is for while they are rolling the die and adding the result. At some point it's just art which you get good at with practice.

Good luck!