Before my trip to Bonaire earlier this month, I thought people who 'believed in spit' as conquerable to commercial defog had to be fooling themselves. Then shore diving fairly intensively, I'd forget defog and use spit.
I gotta admit, it worked at least as well as anything else I've tried. And lasted fine, too; I'd thought it'd rinse out quickly when swishing water in the mask for clearing, but no, not really. This was not a new mask, but it wasn't an 'ancient' one, either.
I'd like to try the shampoo thing sometime, but good to know a fine product is, um, always close at hand. And another good reason to hydrate before your dive (so you don't have dry mouth).
Richard.