Feeling subtle sensations in the body is not difficult. The suggestion here, in order to go deeper in meditation, is to initially feel just slightly below the surface of what you normally feel in the moment. Just one layer at a time. No big leap required! No superhuman feat of discipline needed!
Whatever vibration/sensation that you feel in the moment is fine. It is helpful to have the intention to feel the overall sensation of the body…and to feel slightly deeper with calm “noticing.”
In just noticing the overall sensation of the body, the intention to feel slightly deeper will activate the awareness of the wider “field” of vibrations…sensations that you may not have apprehended previously.
Again, this is not a difficult process. it just requires a willingness to explore the inner landscape of vibrations and to continue just long enough to the point that you are able to apprehend the “slightly” wider field of sensations.
This seemingly “small” incremental step in noticing, is in reality a monumental moment…if you truly “get” the “doorway” that you’ve just created! In allowing yourself to go just below the surface of what you feel in the moment, you’ve created an entryway, a doorway to continue on to finer and finer realms of subtle vibrations!
The dance has begun! Little by little, in feeling subtle sensations/vibrations, you will begin to apprehend the very fine “currents” moving through the spine, body and “sacred space” of all that you feel/experience!
You will have then established a very different relationship and understanding of your “Life Force,” as well as with your sense of “Self.” Your connection with subtlety will become more and more like a dance, a push/pull/play of exquisite sensations moving through the spine and rest of the body!