When I have tried to question beliefs even subtly, JWs always go very defensive and I don't feel as if I've achieved anything. It usually needs to start with them questioning something or at least wondering about alternatives. My post was about using a line of questioning that they haven't already been given an opinion on. Hopefully it could start off an internal process which would lead to them genuinely questioning doctrine. Or not in most cases, but if it helps some, it's worth trying (and is low risk)
SF