What is the purpose for the breathing technique you teach—in through the nose and out through the mouth?
This form of breathing moves vital energy through the chakras and it keeps the central and governing meridians, which meet in the back of your throat, connected to one another. Breathing in through your nose brings a force up your spine (governing meridian) that is fed by each of the chakras, and then shifting to breathe out our mouth creates a connection at the back of your throat which stimulates central meridian.
I see value, however, in many of the techniques that are used in traditional healing and yoga practices. These vary according to the purpose of the breathing, and they also vary from individual to individual. I even see value in "not breathing"—in the shallow breathing that sets off an alarm for many healers. When a person goes into an almost stillness with the breath, he or she may energetically have entered an altered state that can be very healing. Some exercises also have a stronger impact on the body when the person stays in that stillness of breath. A yin force is activated, and along with it, receptivity.
Anyway, it isn't that one way is right and one way is wrong, but rather there are many forms with many purposes. And sometimes it is important to just trust the energy that begins to lead the process when a person is not controlling the breath. While the healer’s attention to breath is often to change habits that keep people from getting the oxygen they need, I personally have on occasion wanted to slug a healer when I've been the one on the table and been told, "Take some deep breaths now." This has felt like a violation of my own rhythm, imposing a more yang rhythm. At other times, however, it has been helpful, so the main guideline is to stay closely attuned with your client and with what you are wanting to accomplish