all this is based on my experience of course....
Is denying everything ever a successful strategy?
In virtually all the cases I served on, the person confessed. So there would have been no purpose to denials afterward.
In the case there is no confession, there has to be 2 or more witnesses. If there are those witnesses, their testimony would likely supersede any denials of the accused.
So no, denials would virtually never work, and would probably lead to a swift DF.
Does addressing a letter to the elders threatening legal action if they disfellowship ever work?
I have no experience with this, but I've read on this site that such a letter prompts immediate reaction from the WTS, and based on the experiences recounted here, it seems likely that the elders would back down.
That may depend on circumstances, though. For example, I suppose it would be more likely that they would back down if the accused had not been associated with the JWs for a long time and thus their relationship with JWs was more tenuous.
Or is feigning complete and utter repentance the only game in town if you really want to avoid being disfellowshipped above all else?
In my experience, if you want to avoid DF, this is the best bet.
The best way to feign repentance is to go on and on and ON and ON about your "damaged relationship with Jehovah" and how you have "brought reproach on his name" and how you have sullied his reputation, and oh how much you want to repair your relationship with Jehovah, etc. etc. etc.
Work "my relationship with Jehovah" into your comments a dozen or so times, and you should be OK.
Any other tips or insights you can think of gratefully received.
They say that "there is no such thing as an automatic disfellowshipping" but there really is.
Here are some things that will lead to DF 99.9% of the time:
-- If you have repeated a "sin" numerous times, received counsel, weren't DF'ed before, but have done it again
-- If you have committed a "notorious" crime that brings the notice of the media to your case and/or embarrasses the WTS
-- If you have committed your "sins" over a long period of time (e.g. having an affair stretching over several years)
-- Lying to the judicial committee then getting caught in the lie
-- Active "apostasy"