I saw a reasonably looking video about a non-pilot trying to land a plane with the help of a flight control tower (in a simulator):(it is in French).
I believe that this was an ideal case where the plane was compatible with the airport so that the landing was almost automatic (they showed a short version of (successfully) trying to land without the automatic mode).
The person in the control tower was extremely knowledgeable about the plane, explaining exactly where to press, where to look etc.
Assuming that the whole exercise was realistic - how likely is it that there would be someone handy who could, by heart, explain via the radio what the exact steps to take are?
Note: I realize that the situation will be different between a large airport (where they could make an announcement "we are looking for a Boeing 747 pilot, please contact the reception desk if you are one") and smaller ones. In the video, they started from a cruising altitude and it took minutes to go from "there is nobody in the cockpit" to "listen to me carefully, I will guide you". It is more the realism of time which I am trying to assess.