Best way to ensure sync between 2 or more cameras is to send reference (black or tri-level) to all the cameras Ref (or Gen) inputs. Then, send timecode to the cams timecode inputs. This will hold sync all day and have synced timecode. With just 2 cams you can use composite video out from cam 1 to Ref in Cam2, and timecode out cam 1 to timecode in cam 2. For short scenes you can use a slate at the start of the scene, and/or use FCPX multicam or Plural Eyes to match the audio tracks from both cams. That will hold for short scenes and then start to drift. If your cam doesn’t have ref in/out or timecode in/out, you’re stuck with syncing with audio. Feed the same audio to both cams to get best results. When the tracks start to drift, blade the tracks and re-sync.