A lot of these video clips of cat hookups / shots that I see on line these days show a qualified "shooter" training someone to also become qualified - that is why you see two people looking like one is parroting another. The qualified shooter or hookup person is the one that must affirm the proper signal for an event to happen - shuttle to take tension, engine runup, fire. etc. People are always getting trained as replacements, etc. Sometimes you may see a JBD topside man in training -- signalint to raise and lower a JBD