TA, I'm an ATC.
I can say with reasonable confidence that you can probably forget about the likelihood of the average controller being of much more than very basic usefulness when it comes to "talking down'' a complex airliner with non-rated pilot flying.
Most of us would have an idea of how to operate a light aircraft (decreasingly so, as flight training hasn't been part of the curriculum for most ANS providers for some time) but a 738?
Forget it.