I have to admit I'd recommend a Timsert\Cal Van over this method now in Nov 2022. I did a 2nd insert plug and went to deep but didn't realize, it melted off part of the insert and broke a valve, changing the head is a 14hr job or more. the Timesert is pretty pricey but they are perfectly made and can't be inserted too deep. If you take your time you can do it this way effectively (this one I did is still working 5 years later) Just be sure to use the exact right insert that has the right amount of threads.
