I used to sync everything manually. Sometimes it took literally hours (I can tell if it's off by only one or two frames). Fortunately now Final Cut Pro X has automatic syncing capability. I can take a two hour hour video file and several audio files, or conversely a long audio file and multiple video files, select them all, hit "sync" and a few minutes later it's done. Magic. It's accurate, too. Once that's completed I can adjust for sound delay if necessary, easy to do as that is constant throughout the show.