The discovery of space begins with shi-nè. Shi-nè is the practice of letting go of our addiction to the thought process.
There is no special breathing technique. Just let your breath flow as it will. At first you should simply find the presence of your awareness in the inward and outward movement of your breath. If thoughts arise do not try to block them. Just let them be. If thoughts drift away do not detain them or grasp at them. Just let them go. Rest your attention in the movement of your breath. If thoughts come and go, simply allow them to lap like the tide.
p38 and p85, Spectrum of Ecstasy, Ngakpa Chögyam with Khandro Déchen, Aro Books, 1997, ISBN 0-9653948-0-8