Unless you need to wash a wound, Woodsman is right, use your water for drinking.
Now back to this shower thing:
Here's the way to do it:
Lay down a face towel under a pail or basin. This catches clean water at first that you may need for scrubbing later.
Pour half a gallon of water into the pail. Hopefully you keep short hair in the bush for extended periods.
Turn your head upside down over the pail and wet your hair being careful to keep runoff going back into the pail.
Soap hair enough to cleanse and use a smaller cup to keep rinsing your hair to get the majority of soap out.
Now use the other half gallon sparingly to rinse your hair out even more.
Make sure all the soapy water keeps running back into the pail.
Take a small sponge and bathe starting at your face using the soapy water in the pail, trying to keep as much water in the pail as you work down to your feet.
When all done scrubbing down, take what is left of the pail water, soap and all, and pour it over your body excluding the hair.
Towel dry immediately to help remove any other dirt, soap, and water.
Then use a non-scented oil or lotion for a skin softener.
1 gallon of water today ........ find me a river tomorrow.