Looking for a Good, Online Bluegrass Mandolin Tutorial Series

What are the best online series for bluegrass mandolin?

I am pretty good at picking through fiddle tunes at a good pace but I am looking to round out skills for when it's not my turn to solo. Crosspicking through chords, tremolo and when to use it, etc

I am debating on a private teacher or an online series but I like the 'learn at your own pace' of online lessons as well as the ability to rewatch or revisit topics.

I'm all for private coaching - it provides a more personalize touch than static one way videos while still being able to provide you references you can review later (i.e. recordings of the lessons, custom sheet music, etc).

That said, there's a lot of online resources that are great including
+ Artist Works
+ Peghead Nation (my favorite of the video ones)
+ https://www.mandolessons.com/
+ my site (shameless plug) https://mattcbruno.com/weekly-posts/

and a lot more. The static stuff is great, but it's not going to be tailored, so you'll need to do some digging.

I've tried a bunch of the different online bluegrass mando course, and to be honest, most of them don't focus a ton on playing rhythm/back-up beyond basic chop chords and open chords. It's actually sort of a missing piece in many courses. Mike Marshal does have a few cool lessons on his artist works course on how to play fills behind a vocalist. But if you want to go in depth on that front, a few private lessons might be the ticket. And if you do them with a teacher over zoom/skype, you can always record the lesson and re-watch when practicing on your own. Just my two cents!

I would agree with what some others have said - playing "fills" and ornamentation while playing rhythm is pretty specific. I feel like Matt Flinner has covered that in some of his lessons.

My favorite online series has been Chris Henry's Monroe Improvisation Workshops. (NFI) But checkout his website Noya Mountain music. There is great content there for learning true bluegrass mandolin, Monroe style. He also offers workshops that run every few weeks where you work on playing specific solos to songs. Included is are the video materials from him, a Zoom Workshop with the class, and a 30 minute Zoom 1-1 lesson with him. That would be a way to get the materials to work on and the 1-1 instruction. It is a deep dive by there are some beginners and people that started as beginners in that group. One of the great things about those courses are he teaches you to slow down the music and pick out the notes on your own which you could certainly do to teach yourself fills and ornamentation, eventually.

I use the Peghead nation courses quite a lot, but mainly to learn variations on fiddle tunes and to study Monroe solos (Mike Compton's Monroe videos). Fills and rhythm playing don't get a ton of attention, though Sharon Gilchrist does have a few lessons on both. She is an excellent teacher. Cross picking never comes up and is a somewhat specialized thing. I'd suggest finding a teacher who could work with you on that stuff.

FWIW, the artistworks format is not static. There are static lessons that may or may not be of use to you, but you are also invited to post videos to your teacher, who then posts a response video. It is not a live interaction but I find it is still quite helpful. Mike talks about crosspicking & backup sometimes as it comes up in questions, but he would focus on whatever you are interested in working on. You can hammer away on the same topic over and over again if you like. I have found him to be quite generous in the time he takes in his response videos, given the cost of the course. I have not taken Sierra's class but I expect it would be a similar format. There is usually about a two week lead time between a student submission and his response. NFI. Good luck on your search.