Trance is an outpost toward stars. An aspirant must understand its nature, which is about all, natural, and easy for every soul. There is no mysticism in this occurrence, just a divine combination of biological and natural processes of the brain. Using methods that requires hours or years just shows that we do not understand the very mechanism of trance, as well as the mechanism of our mind.
Vibration is a signpost to the stars. It does not carry energy in itself; on the contrary, it carries consciousness and serves only to direct energy, which in that case, unmistakably runs toward the field of action.
There are only a few more practical tips related to the mantra; when you repeat it, imagine there is a dark cave in the center of the chakra.