I started flying thumbs, I couldn't separate controls and kept adding unwanted mixing (eg. pulling up elevator netted some unwanted aileron).

I've been flying finger and thumb "pinch grip" ever since and never looked back. I'm trying to transition to a tray but it's one more thing to pack and moving the TX from the case to the tray and back is a bit of a pain.

Fwiw, I fly mostly with a neckstrap about bellybutton height. pinky under the Tx, next two fingers for switches, finger and thumb on both sticks.