steeltarrow wrote:I suppose I just need to keep trying and build up enough concentration to be able to perceive the more subtle feelings that I suppose must be present in the hard spots.
As I understand things, the instructions basically call for using interoception to pick up the general fascia of the body alongside the baseline intero-proprioception of breathing. This happens all the time for most people, to a certain extent, so the trick is simply sustaining a broad & encompassing awareness - try picking up the sensation of blood flow here and there, for example, or various internal organs or internal heat. Get a sense of the fascia hanging on the skeleton. It's quite fascia-nating.
The third step in the second tetrad & the first step in the third tetrad are similar, though not grouping aspects of the body but instead grouping more ephemeral experiential qualia (feelings, the mind).