Lama Ole’s answer:
We do have a meditation that enables us to use deep sleep. We also have meditations for the state of dreaming, but those are a bit dangerous because they work with the throat center, where a lot of very mixed energies lie. If one works with the throat center in the wrong way, one starts to talk harshly and snappishly.
But the deep-sleep meditation works with the heart center. Here, one cannot make mistakes because this energy center is well rounded and in the middle. It can bear a lot and is unshakable—really solid and strong. However, one should take refuge before doing this deep-sleep practice called the “clear light meditation.” In this practice, you learn to become more and more aware and able to take the feeling of dreaming into the day. This protects you very, very well!
I myself received the transmission for this meditation from the 16th Karmapa, but it stems from the 15th. With this practice you can learn to remain in the clear light during the night and to feel at home in it. You do the meditation before falling asleep. It is easy to hold the awareness before falling asleep and while lying down—one can learn both. But to stay clear in the moment consciousness goes from being awake to sleeping, that is the difficult point. But you also don’t necessarily need this.
In any case, if you are working with a machine the next day and you want to take all ten fingers home with you, then you must not do the clear light meditation too often. In Tibet, where people often had to walk long distances with a horse in front, there one could afford to do this. But for us today, maybe just once a week is good.