In Soto-Zen Buddhism there is a sitting meditation known as Shikantaza which is the art of just-sitting. My question, what techniques are given to Soto-Zen practitioners to prevent the mind from being "sticky" or "stuck" during Shikantaza. For example,
I have been told by some practitioners that they would call sight, sound, taste, touch, smell and mind as objects. By referring to the six sense organs as objects they disconnect themselves from the object to prevent the formation of subject. Although it sounds interesting that doesn't sound like, at least by what I've read, as Shikantaza.
Another practitioner told me they simply listened to silence or emptiness. This reminded me of Eckhart Tolle's meditation instructions especially given in his book "Stillness Speaks". The problem I find through this method is the practitioner is focusing on an object, as Lao tzu mentioned in his book the "Tao Te Ching"; the form which is formless. Also, Dogen encouraged the sitter to just sit with no attention to a single object. Concentration on emptiness is neglecting sitting and the original face.
Finally, another practitioner explained he would simply try to keep his attention centered as if he were sitting inside of a dome. That is, trying to be aware of the world and his thoughts while building a kind of cushion between himself and object. Almost but not exactly a combination of the first two.
Therefore, what are the steps Soto-Zen practitioners are encouraged to take in order to practice Shikantaza. To clarify, I'm not interested in physical postures such as sitting, hand positions, the position of the tongue, etc... but rather, what is the sitter doing with his/her mind and the steps they are taking to separate subject from object.