After reading all the stories about people not having showers for days on the trail, especially in summer, I have decided to take a 2 liter sunshower with me (weighs 3 ounces).
I have used it a lot camping and you can really feel clean that way. I mix camp soap in my drinking cup with water for shampoo, and have my cooking pot filled with warm water. I open the shower and just wet my hair, then turn it off, and pour the soapy water from my cup onto my hair. There's enough in there to get two good latherings. Then I rinse my hair with the shower. Next I put camp soap on my cotton hankie, dunk in the water in the pot, and wash down with that, then rinse with the shower. There's just enough water in the shower to get all the soap off.
It makes me feel like a new person -- and really lifts my spirits!
You could wash up without the shower, but I find that I usually end up skipping the shampoo when I don't have the shower. And clean hair feels SO good.
I also ordered a 6 liter food bag (weighs 3 oz.) from Campmor, which is basically just a heavy plastic bag with handles. I will use it to carry water and also as a laundry basin to hand wash shorts, shirts, socks and undies when the weather will permit drying.
I think those two items will make the hike a lot more pleasant for me.
The shower and food (water) bag together weighs about what a package of Wet Wipes weigh and they are reusable.
Hope these ideas are useful.... but I guess the 6 ounces means it won't do for ultralighters!