The only short pair of underwear I carry is flannel boxers, which are cotton. I think one pair of flannel boxers is quite manageable. If they get wet, I take them off. I use boiling water from my Kelly Kettle to wash them. I wear them on my head to dry them. Wearing them without anything over them works also, either alone or over a long skin layer instead of my hiking shorts. They are plaid, so as long as you do up the button they are quite respectable in the event of a chance encounter with civilized people. One piece of cotton is manageable. Two is a pain in the butt.