Nearly every tutorial I've seen on making clothing stops at the point it resembles the article of clothing and doesn't cover mechanical movements like fastening/unfastening. Shirtfronts and cuffs unbutton, bras unclasp, hoodies pull back the hood, pants unbutton and unzip, etc.

Looking into the .cr2 files of conforming clothes that unbutton, I loosely understand how they're constructed (creating dials that run morphs whose deltas are inside the .cr2), but as to how those items are modeled and the .cr2 sections created, I haven't a clue.

Can someone help me out here?