(In my experience). Mention how you feel like a hypocrite in preaching to others to look into their religion. If you were a born in, then you never had done any investigation. There is a phamphlet (Forgot but maybe somebody can link it) that was geared towards those of other religions and said if a person was born into it, even if it was the true religion, it wasn't sincere on their part if they never investigated to make sure. (This phamplet from the org is the big green light to do outside investigation, even though they didn't intend it for insiders, the elders can't say that they are preaching hypocrisy, etc.)
Also if they asked about the faithful slave, tell them you believe in the bible and what it says. Also (it will be easy since it's sincerely confusing for everybody) tell them you are confused about what it is too. You can really answer many of their questions with questions if you know your stuff and they'll get confused and put it aside, especially when many of the flip flops. Asking to show in the scriptures how the current overlapping generations is explained through the bible, and what in the scriptures lead it to be those 15 and over in 1914. To those born in 1914......then to nobody should try to answer it because Jesus says nobody knows the day or hour, then back to overlapping generations. To show and explain what in the scriptures supports those changes in belief.
In the end, it will become they'll assign one to try to answer your questions. May last a month or so and something comes up or too busy. Then gets to be a yearly phone call.