I have used Kirk's Castile in the past, but I had to use a vinegar rinse to get all the soap out (hard water issue); same with Ivory soap.
When "not looking decent for six weeks" isn't an option, at least the soaps have less crap chemicals in them. BTW, I wore my hair short most of my adult life and have only grown it out the last couple of years (shoulder-length). In a true SHTF scenario, I would cut it short in a heartbeat (less hassle)---and I always cut my own hair anyway; a pair of mirrors , good scissors, and twenty minutes, and I can go anywhere.
"You're not living in the story the world tells you you're living in. The story is not about the Clash of Civilizations, the March of Progress, the American Dream, the Rise of Civilization or the Struggle of Race, Class, and Gender. It's about the triumph of Jesus Christ in rescuing us from this passing world and bringing us into eternal ecstasy and perfection."---Mark Shea