Q: If you’re using more than one chalice, should you use more than one pall? And would you take them all off and put them all on at the same time?
A: The rules aren’t very clear. The GIRM invites us to have a pall ready, but then never tells us when to use it. The Ceremonial of Bishops provides information about the traditional usage. Usually a pall covers the chalice after the preparation of the gifts, is removed for the epiclesis and consecration, replaced, removed for the concluding doxology of the eucharistic prayer, and then replaced again until time for communion.
I use a pall only for its original purpose: to keep bugs away from the chalice. If I don’t have bugs, I don’t use a pall. If I do have bugs, and I have multiple chalices, I cover all of them with a pall for the same reason. But there’s no clear rule.