I use charcoal for a few reasons, but not that often...they are:
1) If cold smoking (110-120*) my cured jerky prior to drying, I've added hot coals for some heat and to get the smoke wood going without lighting the burner until I begin drying the jerky. When using this method I only use 6-8 briqs depending on ambient temps, wind, etc. I place the briqs touching each other, but not stacked, and put smoke wood touching the edge, while sometimes putting the wood on top of the briqs if I need, just to get it smoking;
2) For added flavor, as there is a noticable difference between chacoal fired and propane fired smokes, IMO. In this case, I keep the smoke wood(s) seperate from the charcoal unless I need extra heat to get the smoke wood started. Mostly, I just crank the burner to high flame when I start the smoke until I start smelling smoke, then back it off to reach the desired smoke chamber temp;
As for the actual smoke from the charcoal, I find it's best to get the coals heated up (if not burning) before adding any meat to the smoke chamber. Cold briquettes give off a very strong (and rather foul, IMO) smoke when they first get hot. Once that initial smoke has passed, you're good to go. I don't like to add cold briqs to the fire box in a charcoal smoker for this same reason. I get them at least to a partial burn in the chimney first, and this releases that initial smoke pretty well.
Eric