We attended the Phildelphia Folk Festival when they had their 25th Annual show. There were some bluegrass artists, but the performer we remember most was Elizabeth Cotton. She was very old at the time, and died not too much later. She wrote the song "Freight Train" when she was 12, and it was like a one hit wonder that she continued to perform at Folk Festivals until her death.
I kin play "Freight Train", but not upside down like Miz Cotten did. ;-) She was left handed, and played the guitar upside down.
I have a hard enough time playing it right side up!
I bet you'd like Vassar. Not really straight bluegrass, most of his stuff. Jazzy and bluesy, too. Just good.
Check out some sound clips on Amazon when you get a chance!