Quiet the mind, still the heart. Focus on the breath, examine the light. Use the backward flow to return to the source. At times it is cool, other times, warm. Nothing to moderate or massage, just circulate Qi and the Light.
Yin Yang with extremes reached shall interchange. So will forms and emptiness. Like what Laozi said in Chapter 14, there is nothing to do, except watch the transformations. With continuity, you could reach the Center or Tai Qi as described in his Chapter 6.
When phenomena clear, gates can appear. Depending on aptitudes, travelers may have occasion to approve of Zhuangzi who related the travels of Daoist immortal, Guangchengzi and his student, Huangdi who had curbed evil and furthered good.
If you ever doubt what is seen, take a walk on the wild side and visit the Stars gallery! A visual advantage proffered by science over ancient descriptions.