I think we must clarify that while there are many practices to improve health, Master Ou does not advocate raising body temperature as a matter of general practice, it is not a part of the 5 practices. Naturally, if a person is cold (yin dominate or yang deficient), particularly in the winter months, then some heat to make the person comfortable is a good recommendation, like drinking hot tea, but we generally do not consciously know what our body needs on a subtle level.
In addition to a feeling of warmth, a feeling of coolness is often experienced during practice. Master Ou indicates that such sensations of heat are related to the sun qi and sensations of coolness are related to moon qi. I would hesitate to recommend, "Continue to elevate your body temperature to a point that you feel physically uncomfortable" in the context of healing. This could in fact be counterproductive for some individuals. Although sweat therapy and saunas are known healing modalities, and very good generally for purifying the toxins from our bodies, there are individuals who need the cool yin energy more than heat for their healing. Some qigong practices do use tumo breathing to raise body temperature; Tibetan monks are known to be able to stay outside in the winter and even to dry wet icy towels placed on their backs. Again, not a part of the 5 practices!
I love bringing to mind the password, or some of Master Ou's songs or poetry, even the image of Pangu, particularly after the non-moving form, keeping the password close to the heart, literally thinking from the heart area, seems to change the world I see.