@Glenn Vilppu and @Steve Huston are most certainly two living masters to study from! One thing I love about the old masters studies they do at NMA is when they narrate and analyze what they’re drawing. Of course just copying their demos can be a masterclass on its own, but listening to their insights and thoughts on the art they’re studying is priceless. I’m currently watching a series by Steve on composition and it’s already blown my mind so many times. And I remember one of the most valuable tips I ever got about how to hold a pencil with an overhand grip came from Glenn at a workshop, many years ago, where I had the chance to watch him live: I saw him sketch with arm movements so freely, yet his lines came out so light and controlled, and I was like “How??” And then he said he often slides his fingernails on the surface of the paper - it gives more stabilty than letting the hand be loose on the air and allows you some support so not to put pressure on the tip of the pencil. 🤯 As far as living masters from which to study linework and pencil grip, besides Glenn and Steve, I’d also add to Elson’s list many other names, among which there would definitely be @Mike Mattesi, @Jeffrey Watts and @Stan Prokopenko!

Gustav Rehberger is an artist I have recently found out about whose figure drawings and mark-making are filled with power and energy. Some videos of Rehberger working have been recently posted on YouTube -- the sound and video quality is lacking, but you can see him working with the overhand grip. You can check out some of his drawings here: https://www.gustavrehbergerfineart.com/drawings

You might also look at Raphael's drawings. His studies are remarkable. But you won't see him on video actually execute the line. There are some really excellent images online of his preliminary studies, the Royal Collection Trust has some images that are really well imaged - https://www.rct.uk/. (Raphael's study of his "Massacre of the Innocents" demonstrates why he is a master) I really appreciate that you did this research to answer your own question and shared it. Thank you for that.