Making wine

[Epictetus]

I have a few questions about ancient wine-making that hopefully someone can answer. I’ve been reading Longus’ pastoral Daphnis and Chloe and came across this passage:

This one was busy with a small hook for cutting the grape clusters, that one was looking for a stone big enough to crush the clusters of juicy grapes, and another hunted for a dry stick smoothed by blows so that the must of the grapes could be carried out at night under the lead of a lantern… Daphnis lifted grapes in baskets and emptied them into the presses and stomped on them.

First, if people stomped on the grapes (I suppose the traditional image of wine-making), what was the big stone used for? Was it used before stomping, or after, or what?

Second, what is going on with the dry stick? I assume the must was beaten with the stick, but I don’t understand the phrase “carried out at night under the lead of a lantern.”