After the failure of the hot water method, I tried hot water plus a tiny amount of shampoo around the hair line.
The result was better than hot water alone. I didn't feel icky until the evening.
Better....but I still didn't want to have to wash my hair every day for an untold number of months while my scalp adjusts.
I began to realize how shampoo was actually harming my hair, though that wasn't the impetus for going poo-free. Right after cleansing, I realized my hair wasn't nearly as frizzy or dry as it normally was after shampooing. Interesting.
I've read claims that shampoo causes the scalp to react with an overproduction of oils, and the shampoo-free project has a long adjustment period as a result. There really does seem to be something to that claim.