I also have a classical background as well as years of using a pick. In the last few years I've found myself playing guitar parts that would normally be flatpicked with my fingers. I alternate using thumb-index finger and/or index finger-middle finger to get the speed of down up picking.
I started out in about 1960 using the Carter scratch, and soon played some eighth note runs using thumb for on the beat notes and index for off the beat. I still do that around the house sometimes. I like to do the finger style that I learned from Libba Cotten, Dave Van Ronk and John Hurt LPs as well.
Again, I have a finger style classical guitar background BUT, these days, I always have a plectrum in my hand ( I'm pretty good at hybrid picking). I would suggest that you truly immerse yourself in plectrum playing ( if you want to play bluegrass ). Live with plectrum. Have one in your pocket all the time, and get it out now and again and just figure it. Make it part of you. I love the plectrum for it's volume and articulation, but, when playing solo with a plectrum, I often strum with my fingers ( which is a folkie sort of of thing )