I haven't seen anyone mention it here, but one of the most productive tools in the FCP aftermarket is PluralEyes by Singular Software.
It works INSIDE FCP as a multi-cam video syncing program that works by analyzing the AUDIO tracks of multiple camera takes and aligning the various camera angles by using the sound waveforms. This means that it DOES NOT require timecode of any kind - and it also successfully syncs multiple cameras where they have been started and stopped randomly.
All you need to do is properly set up the ANGLE information in the FCP timeline database to properly identify your multiple cameras and then invoke Plural Eyes and take a break. When you come back, the various takes and tracks should all be in sync and your multi-cam timeline built.
It's almost magic.
Remember, FCP would not have nearly 2 million paid seats out there if it was actually hard to use or counter-intuitive. Yes, it's often hard to re-train yourself - particularly if you've already trained your brain to think in ways that another NLE does things. But the entire television, movie and indy film communities couldn't ALL be duped into thinking FCP is a great tool - if it wasn't.
Hope this helps.