"It was, you know, incredibly strange as an actor to have to cover your face to rehearse, because it's sort of counterintuitive to everything that an actor needs to communicate. So that part's weird," Janney said.
"It wasn't easy in the beginning, but now we know we just do it," she added. "I get tested two times a day. And for the rehearsals -- I mean, the run-throughs, we're allowed to take off the masks and show everyone."
Janney said the cast and crew are separated into different zones and wear contact tracing trackers while on set.
"They're so great, the way they've done it here," the star said. "We all have different zones. Now I have to wear a tracking thing so they can tell if I've been in contact with someone longer than five minutes who was outside my zone.
"I'm just grateful that we're actually able to work during this time. Not too many people have been that lucky," she added.
Janney said she enjoys taking the type of COVID-19 test that requires a deep swab up the nose, which Late Night host Seth Meyers agreed with.
"I do look forward to it," she said of the test. "Some of them don't do it hard enough. I'm like, 'Can you do it a little harder?'"