I take cues from my cats and the original Cat Woman (Michelle Pfeiffer, oh baby), and give myself a tongue bath. It works for them, why not for me? Granted, the logistics of licking me nether regions is both difficult in practice and.... conceptually doesn't quite sit right with me either.
More seriously, i rarely get to get out for longer trips, but if i were, i would get a flax linen or hemp fabric, small face cloth. (I use a linen towel and bathrobe in regular everyday life, and these stay pretty "fresh" for a long time.). As an alternative, a polygiene treated small poly towel/face cloth would work well too, but can build up oils in same, eventually leading to some stink via non microbial causes.
That with a little good soap, some water, will go a long way. For extra freshness and antimicrobial properties, one could throw in a little (a pinch of) borax powder (dissolved in plenty of water!).
The last semi long trip i did, i *****trimmed***** my lower fro down (don't shave it completely, please just don't), as well as shaved my head shortly prior to said trip.