There are 84,000 Dharma gates in Buddhism. Each gate leads to sudden enlightenment. But one who has experienced this is said to be "like a mute eating a bitter melon." The lightning like experience of wu (Japanese: satori) -- also called "sudden entry as if with a sharp cleaver" -- cannot be verbalized.
Also, it is well known that any student who attempts to enter into the depths of Zen without having first developed some meditative stability is liable to go insane. The use of sexual expedients in particular is not recommended for the shallow or the weak-minded.
"Cut off thinking; keep unmoving mind." This takes power and fanatical dedication! As the Chinese Masters used to say at the end of every Dharma talk: "Please take care of yourselves."