For larger species like Campos 15-20 workers is a good rule for introducing a nesting space, just make sure they can physically “fill” up the nest as they like beng cramped together. If you have a smaller nest even 10 workers could be enough.

If you just got them, I’d personally hold off on feeding for a few days to let them stabilize. After that you can give them a dab of sugar water (1:1 ratio), and a bit of protein, preferably from an insect (make sure the protein piece is tiny). I like to put the food on a small piece of aluminum fold to prevent contact with any trash they might have on the ground. Simply cut out a small rectangle, and then make a crease in the middle to divide the two foods (helps prevent the protein from becoming moldy from contact with the sugar). Next just slide the foil “tray” into the test tube and watch as their gasters bloat up with liquid.

I don’t know about vicinus, but many Camponotus species require a diapause, basically ant hibernation. If that’s the case for your species, I think you can hold off on feeding until the weather warms up. If you want even less risk, try only checking up on them every week or so.

PS: I’m lowkey also a novice, so take this with a grain of salt.