No Explaination Required!
The guy playing the mandolin in this clip is the son of my cousin. He’s a true music genius, can play any instrument he puts his hands on. Makes me jealous.
Peaches and Cream was one of the very first bluegrass songs I was ever introduced to. I should really take the time to learn that song. It’s really beautiful.
Wait! @BanjoBen, is Alison Brown double stroking her thumb pick in this video starting at 0:41?! Is that even a thing!?
Working on it right now 
If you mean two strings in a row. I do that sometimes, Can’t remember who taught me that trick. Alan Munde perhaps.
I mean it looks and sounds like she’s droning her low D string by doing a down - up - down- up picking motion with her thumb. I can barely just do down strokes. Do I have to worry about learning up strokes, too? 
I have never tried it and I have no intention to do so 
It sure looks like she is! I’ve never tried it or seen it, I don’t think, but now I wanna try it! @Archie, he means play a down and upstroke with the thumb like a flatpick.
I have friends that do it on guitar, or course, but not banjo.
I saw a video of Bela Flek doing it, but it wasn’t droning. He was somehow just fitting it into the song. Then again, that’s Bela.