Out of curiosity, what about VC papers helps you "dig" for shadow detail as opposed to graded papers? Certainly, detail that is not in the negative can't be printed, so you are talking about very low values in the neg. How does VC paper allow better printing of these? (I use graded papers for the most part and am not an expert in the nuances of split-grade printing, etc.)
Also, I would think that raising shadow values by pre-exposing B&W film would be inferior to simply adding overall exposure and adjusting development for the highlights, since a pre-exposure, while raising the shadow values somewhat, also decreases contrast in those values (like flashing a print lowers highlight contrast). This, unless for some reason, one was trying to create a negative with less shadow separation and relatively more highlight separation, which seems to me to be the exception. (Of course, with color transparency material, pre-exposure is a very helpful technique.)
I would think that increased exposure and reduced development or print flashing would produce better results in most cases.