Unless you'll be rendering some extreme closeups, I'd probably just go with a bump map for that. Select the polys in the waistband and apply a cylindrical UV to it, use an image of irregular vertical lines across the horizontal length of the mapped area.

If you really want to model the geometry, it would have to be pretty dense as the folds/wrinkles would be very close together, and a lot of them. Not familiar with Hex myself, but from a general modeling standpoint the "gear primitive in Sub D" (with a lot of teeth on the gear) would pretty much be what you'd actually be doing.

Like a cylinder with every other row of points pulled outward slightly from the rest. Then manipulated slightly so they wouldn't be all too uniform looking. If Hex has a noise or jitter feature, that would make quick work of the non uniformity. If not, just random selection of points in the area and slight moving and scaling would be needed.

Hey! His nose is dry! ... Someone should lick it,  just in case. - Diego