Spark plug washer and anti-seize

 Because  I can see different answers, I decided to ask again: should I remove a spark plug ring/washer if I use a CHT thermocouple sensor under that spark plug?

 And the second question: Rotax spark plug guys say not to use anything on new "shiny" spark plug thread. A guy on video in this Forum recommends to put some expensive silicon on the thread. So, what is latest greatest recommendations>

                      Thank you very much.Egor.