I'm agreeing with GA, it does seem quite difficult. I sometimes read a fantastic blog on making your own products and
she's done a number of posts about shampoo, but be warned, she definitely doesn't come at it from a natural ingredients perspective (although she explains why she thinks the various synthetics are necessary). A lot of her recipes are entirely natural though (not the shampoo ones).
You can try using handmade soap (either yours or someone else's!) on your hair - this seems to work really well for a lot of people, although whenever I've tried it my hair ends up looking like Sideshow Bob on the Simpsons, but this might be because we have incredibly hard water. This might be worth trying though, in case you're one of the people it works well for. I'd do this if I didn't have the Sideshow Bob issue.
I believe you can also use bicarb & water but I haven't tried this - I think we've got a thread lurking about somewhere!
Good luck with it all

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