guidance needed

I have a cos. Some mods done to it so not that bad. I am new to the smoking game. I have destroyed my first brisket!!:(. I am doing a 9 pound shoulder. What I am wondering is, I started a bed of charcoal and added apple chunks. I am 4 hours in a different have used a lot of wood To keep the heat where I want it. How would I go about adding charcoal and secondly is it a bad thing to rely on wood? I am worried about over smoking it. I have the tbs rocking but still concerned. Thanks for the time.

Pete