The plastic bag with holes will certainly saturate the air quickly bringing your concentration gradient to zero. Dryers work because they continually bring outside air in (heat it up) and exhaust the hot moist air.

To dry things you need flow of air over the wet part of the sock (if you took heat transfer back in the day too: the convective heat transfer Nusselt Number is directly analogous to the convective diffusion Sherwood Number). Attach your socks to the outside of the pack and get as much air flow across them as you can. Jerry-rigging some way to lift them off the pack (or dangle off the side) would be a good idea. Better than the black felt backing suggested above... you could try using black socks. You could also direct sunlight onto the socks by Jerry-rigging some reflective material... but that sounds a bit kludgy to me.