About This Answer
A meditator asks whether, when subtle sensations arise in a calm state, one should scan them for impermanence, as in some vipassanā methods, or return to the breath. Ajahn Dtun calls attention to surface feelings a superficial approach. One can simply stay with the breath, which grows more refined until body awareness falls away and the mind separates from the body by itself in concentration.
For insight he recommends going deeper with one of four themes: death, the 32 parts, the unattractiveness of the body, or the elements. Once the mind has rested in concentration and thinking resumes, take up the body and probe it to see its impermanence, absence of self and unattractive nature, so that attachment to it is let go. Studying nāma-rūpa as theory is only memorised learning; it has to be made real in one's own body.