For me, Rayna Gellert is a superb example. She was exposed at an early age to Old Time fiddle and banjo by her father Dan Gellert and his music friends, and went on to study classical violin. She is now a brilliant soulful old time fiddle player (check out Uncle Earl or her solo work) who unlike many OT fiddlers also has excellent technique. If you've got it in you, training's not going to stamp it out.
Ray