Gernot Hassenpflug

Nice story Don. Mike Sigman and others have pointed out that the internal body movement needs to be "burned in", it is not and add-on skill. Thus, by definition, as you say the unbendable arm will be in everything you do. Since there is a mechanical basis to the internal skills -- they are not magic -- it is fairly easy for practioners to put them to use once they know exactly how they work. It is not as though one needs to "set up" some conditions, at a basic level this is the by-now natural mode of movement and coordination (at a given level of skill and self-knowledge), i.e. the mechanical leverage-based method of moving the body parts.

Edit: Mike beat me to it! So the "burning it" part here is a lot about use of jin, body alignments, rather than pressure useage.