This is quite simple really. Adjust your thumb position until it feels good to you and opens fast. Open until your thumb becomes a bloody mess. While your thumb is healing sharpen your knife. Cut off the hard callus that forms on your thumb. Flip, Heal, Sharpen, Cut. Repeat as needed.
After one cut or two on your thumb you will be a master and it won't hurt at all anymore. Then you can hand your knife to your friends and laugh when they can't open it. Then show them how easy it is to open and how fast you can do it. Hand over knife, Laugh, Show. Repeat as needed.