I use one MAYBE two tennis ball size chunks per cook. Some like more. I avoid the ashtray effect by using the smoke wood sparingly. Anybody can make smoke.
I plan for this to take about an hour: 30 min for the chimney to get volcano hot, then 30 min after I dump the lit lump unto a full ring (within 1" of the top) of unlit lump until the fire burns clean I put it together. Make a clean fire with near non existant smoke ...then add the smoke wood, put the WSM together, add water to 1" of the top of the pan, load it with meat, and let the WSM temps rise and fall.