Direct transmission between teacher and disciple does not necessarely need elaborate words and detailed instructions.
Shechen Rabjam Rinpoche: Once, Patrul Rinpoche was with his close disciple, Nyoshul Lungtok. They were lying at night in the meadow above Dzogchen Monastery.
Patrul Rinpoche asked him "Lungtok, do you know the nature of mind?"
"Not really." replied Lungtok.
Patrul Rinpoche said: "Do you see the stars shining above in the sky?"
Lungtok said: "Yes."
Patrul Rinpoche "Can you hear the dogs barking down near Dzogchen Monastery?"
Then Patrul Rinpoche asked: " How is the nature of mind?"
At that moment Lungtok had understanding.
This is possible with pure connection and so great devotion.
“Sentient beings, self and others, enemies and dear ones—all are made by thoughts. It is like seeing a rope and mistaking it for a snake. When we think that the rope is a snake, we are scared, but once we see that we are looking at a rope, our fear dissipates. We have been deluded by our thoughts. Likewise, mentally fabricating self and others, we generate attachment and aversion.” ~Dilgo Khyentse Rinpoche