Ive heard of people "bustin flocks" before but never actually done it, to my understanding you spook the turkeys into separating then try to call to them as they get back together? Am I right? Is it a fall or spring tactic? How successful is it?

It is mainly a fall tactic however it does work in the spring also.
It is very affective in the fall, useing the kee kee call is very deadly on fall birds.