it's not about manual dexterity. it's about repeating the process of knot tying over and over and over and over and over again. muscle memory.
learn from youtube videos. learn to tie an instrument tie first, then a two handed knot, and then a single handed. do it over and over again. buy a spool of thread and tie knots around the arm wrests of your office chair, around your steering wheel for when you are stopped at red lights, and anything else you can think of. come first day of your surgery rotation, you better know how to tie. don't ever deny an attending or resident by telling them you already know how to tie when they offer to teach. play dumb and then rock their world with your skills.