I believe Samadhi “without seed” may be mental void. And in “Introduction to magic” by Ur Group such a void becomes an experience where the Spirit gets deeper and deeper in a substance which is now dense now subtle, now dark now light… In the same work there is an advice about possibly resign to stay seated or lying down (pretending that it’s impossible to do otherwise) and keep practicing, maybe indeed it’s a matter of longer time?
The conscious mind is programmed to pass thoughts through but meditation is simply applying a filter that the thoughts go to whilst you maintain whatever meditative style you’re approaching. Thoughtlessness exists but so does mindful thinking.
For astral projection I exercise for some days now the imagination of lying counterpart to myself. It’s hard to achieve but I feel my brain fighting to realize the imagination. Time will bring clarity.