Soap is a surfactant. It causes the stuff clinging to your skin to let go so it can be rinsed away. Make foam and rinse it and you're clean. I use a cut-down gallon milk jug as a good little sink when I've set up camp. Not recommended for boiling water, though. A little nailbrush is helpful. Dig a small cathole for the used water and remember to stay as far from any water source as possible.
On the trail, alky handwash and/or antimicrobial wipes (unscented, please!) work well. Keep a spare plastic bag to drop the used wipes into - the hand wipes, not the ones for the other end. (Although if you can't burn your TP at the moment you could pack it along until you get the chance. I prefer to drop a match into the cathole. There are some odors that NEVER come out of a backpack - please, don't ask.)
I can't remember where I saw it, maybe in 'Father' Jardine's writings, but someone cut down a bar of Ivory soap and calls it their 'Ivo' bar. Light, cheap and efficient. I've also seen an article about using a food processor to shred bar soap and mixing it with water to make a liquid soap.
I carry a one or two ounce Nalgene HDPE bottle full of Dr, Bronner's Peppermint. In hot water and applied with a bandanna or washcloth, it helps soothe sore muscles at the end of the day. I also keep a small bottle of Listerine (or the cheaper store brand) in the first aid kit since that kills everything it touches, even athletes foot. Use it to cleanse an area before you put on a bandage or moleskin. Or kill morning mouth.
I've tried the Sea to Summit soap slices and they work OK but they're pricy and a little water in the package makes a mess. I might try going at my Ivo bar with a carrot peeler!
Anybody remember CampSuds? That worked well but I haven't seen it in a while.
Anyway, this is an excellent article (and website)and the comments are by and large very good. Swearing is what I do when I am too lazy or angry to think of better words. Some a**hole told me that a long time ago...probably my dad.
I agree that the illegal immigrant metaphor is lame. Maybe you could have used something along the lines of "cleaning the knife you've used to fillet a brookie before spreading peanut butter on a bagel the next morning". Again, please don't ask...
Hope to see you all on the trails soon,