From last Thursday night's game session, someone asked me "how are you working the NPCs?" He was right to ask. We were playing on-line with only draws to seen from bad camera angles, if not just trusted. I actually held every draw card so everyone could see it. I didn't think to show everyone the NPCs that they were dealing with.
It boils down to this. When NPCs are important to a scene, I draw a card, face down. When I must test his, or her, capability I state the rating. If you've read the rules "One" is the hardest. until somewhere around "7 " being ridiculously easy. I then draw a card for that NPC's effort and flip over the card that I set aside for them.
Now this method can be for singular NPCs and groups, depending on how many card decks the GM has to play with. Since I currently have about eight different stacks, I actually can do multiple gangs of NPCs. Whenever I have to draw on one specific member, I just rule, then draw, and turn that Character's card upward.
I have fully detailed NPCs, complete with Player-Character styled Actor cards. I still use these NPCS, but only infrequently. For the most part, I use one card to represent an NPC, and then I base every success or failure based upon the single card that I drew for them.
That is one way of dealing with things that occurs in the plot of any scenario. Got a better method? Please jump in, I want to read it.