I was able to do it once with the simple exercise of barely typing my name on an invisible keyboard while keeping the rest of my body completely still, only moving the tips of my fingers maybe a centimeter or two. Something about that repeated motion allowed me to keep some subset conscious as the whole transitioned into sleep. It was a very spooky transition! I descended until I felt a cold hand on my shoulder and whispers all around me, crescendoing to me opening my eyes to the lake in the neighborhood i grew up in. The fidelity of the simulation was very high as well, certainly beat my ability to distinguish! Eventually, as i was flying down the street a giant sand worm emerged from a darkness and closed in on me until i woke up. I could control some things but it felt like the dream telling me it'd had enough.