Good charcoal is high in carbon, low in other components. The other components are what is left behind (or what blows away in the wind) as whitish grey ash.
My barbecue has a cast iron tray, with no ventilation holes, so even without dousing, there is a fair quantity of charcoal left in the bottom, with the ash, once it's gone cold.
Charcoal is great, gives very, very little smoke (once it's got going properly), but is very light. You might think that's a good thing when hiking, but it also means that it's very, very bulky.
My 100l rucksack, filled with charcoal, would probably weigh no more than about 5 kilos... but that should be enough to cookl for four people for a whole week.
My idea for a charcoal stove, would be a sort of hobo "paint tin" stove, like I've seen mentioned on here, but with a second tin, that is a close fit around the stove.
To extinguish, you'd put the stove inside the larger tin, and put the lid on. The lack of oxygen should do the trick.
You'd have to leave the stove long enough, so that the coals don't re-ingite when you open the tin, but not so long that it cools down so completely that the pressure inside gets too low to take off the lid. Maybe just a flat plate, placed over the top (a billy can might be enough) would be better than a tightly fitting lid...
Rambling, idle thoughts for a dreary Wednesday morning...
Keith.