Wow, I had no idea that so many people showered (using the term loosely, I suppose) in the backcountry. I generally don't do any type of body cleansing unless I'm out for more than a few days. Of course, maybe that's why I have trouble finding people to go out with me :p . I generally prefer a slight stink over the complications of carrying and utilizing cleansing techniques, particularly when bivy / tarp camping (privacy may or may not be important, but I sure as heck know that I can't shower or wipe down inside my tiny bivy).
Perhaps if you find it sticky and cold inside your shelter, something like a candle lantern to provide warmth and control humidity might be an idea. I've had good luck using a candle lantern in the winter, and it does seem to help with humidity and condensation inside the shelter, but I'm unsure of what mechanism (if any, could be psychological) is at play here.