There was a legendary post on the Big Green Egg forum years ago by Elder Ward (archived at http://www.nakedwhiz.com/elder.htm) in which Ward brilliantly explains how to achieve a long burning, low temperature fire using lump charcoal for a long, low smoke. He opens an entire bag of lump and sorts the coal by size. Clean all of the ash out of the bottom of your grill (especially important for the Big Green Egg where airflow can be controlled precisely if ash isn't clogging the airway). Place the largest pieces evenly in the bottom like a jigsaw puzzle. Use smaller pieces to fill in the gaps. Light with a little square of wax/sawdust firestarter. Following Ward's method in my Egg, I can keep a steady 200 degree fire going for twelve straight hours or longer. Because the fire can't be set off center, I use a ceramic deflector to create an indirect kind of heat.