I always use RO lump. Love it, and it leaves very little ash. And yes, at the end of a cook, I snuff it out. Next cook, I sweep the ash out, light a small chimney of coals and dump on top of the remains from the last cook. Repeat. I have cut my charcoal usage in half by doing this.
BTW, Weber offers a small chimney, of which I use exclusively. The large one I have just sits there and screams, "Hey!! What about me?!!"