I have never considered how much fuel I put in my WSM. It can be at the max load whether doing a 1 hour smoke or a 20 hour smoke. My smokes average (let me check my log) 4.44 hours. When I"m done I snuff the fire. Next time I'm going to smoke I shake off the ash, clean out the bowl if necessary (learning to pick up the grate loaded with used cold charcoal and not spilling it is a nice skill to develop), load more charcoal and wood if necessary, then add my hot coals.
Depending how hot I want my chamber determines how much charcoal I put in my chimney to add to the cold pile in the WSM. If I'm shooting for 225F or so chamber temp, I only fill the chimney up about 1/4 way before I light the chimney. 250-275F chamber temp 1/3 to 1/2 chimney. If I'm going for 325F or higher chamber temp, I load 3/4 chimney or more. I just dump the new hot coals in the center of the pile of cold charcoal, let them burn like that for about 5 minutes with the WSM unassembled, then put it together, open all the vents, and let it come up to about 15-25 degrees lower than my target temp before I start closing down my lower vents. Stabilize, let the smoke start to turn blue, load meat, then go watch football.
Controlling the chamber temp in the WSM with the lower vents is pretty easy to learn. Get it cruising at the temp you want, load the meat, and it is done when you have reached the meat's target internal temp. Do not use time as a measure of doneness or you have underdone, overdone, and occasionally rightly done.
Whole chicken? 325F or higher chamber temp until 165F internal temp in the thigh. Some go to 175F there but I find the breast can get overdone if the chicken is not brined. Spatchcocking the bird will help it cook more evenly.