My teacher has been on my case about my bow hold, and frankly, I have to agree with her. Below, Perlman explains his own bow hold. What I find interesting and elusive is how he keeps his wrist flexible.
You can see the springy pinky action I'm after in this part of Shostakovich's Piano Trio in e Minor played by Gidon Kremer:
My problem: I can't even reproduce it once, much less practice it. My wrist is dead as a doorknob, and my pinky is equally stiff. When I try to relax it even more, other parts of my technique begin to fall apart... What is the secret? How can I practice it?