Also, most all my clothing is listed in sub-directories under the "Figures" menu in the library. That is both conforming and dynamic clothing.

Dynamic clothing is usually in the Props section. And no, you cannot conform it. Conforming clothing should be in the Figures section.

I've been mostly dealing with Don Nude Hi Res. An example of the clothing piece I've tried putting on him is the P5ManNehruCoat_1....

I don't think I've ever used P5 man or his clothing. And I don't have P5 on this machine, so I can't check. Did this item come with Poser 5? And are you sure it's meant to be conforming clothing?

I've been to poserfashion.net but have yet to find anything there that is very helpful as far as tutorials go.

Download a free dress from their P5 section. It comes with instructions on how to use it. Dynamic clothing is very different from conforming.