Assuming water to be in limited supply [edit: and that you have hair to clean], how would you clean your hair in a longer term emergency?

I have tried rubbing in and brushing out corn starch - horrible mess and never quite out of the hair. I looked at a spray product but I never achieved the "separate each lock of hair to get spray to roots" thing, and I did not like the spray migrating around. I have seen advertized something called "No Rinse" that you rub in and towel off, but have not located any yet.

Thoughts?

Thanks.