There was a thread a few years about using a thumb pick for chicken pickiní wherein Valvey said start with (translated for hybrid rather than thumbpick) the ring finger. That does have some advantages in that it gets the comparatively clumsier ring finger into the mix at the get go; so far I can keep it mixed in better if I get it in there before the middle finger.
Originally Posted by Valvey
I found the biggest hurdle switching from a flatpick to thumbpick style is playing runs with more than 2 notes per string. So I practiced ad nauseum The Flight of The Bumble Bee, mainly using the picking pattern: middle,thumb,index, middle,thumb,index (Atkins apparently used this pattern, as does Mason, although with ring and middle finger instead.) A little wrist action keeps the pattern going. Short nails seem to work better for me. You want to prevent the thumbpick from dominating the fingers. Using a lighter thumbpick helps. I use a Herco medium.
Here is thread if anyone wants to see it: