Jason curious to see if you have tried to top off the chute say when it's still half full to avoid the dirty smoke problem?
The one and only time I added charcoal it was about 1/4 full, and I brought it to half full. I had it set to 225 at the time, and it took about an hour for the smoke to clean up.
I noticed this on other charcoal cookers as well. Putting cold charcoal in a hot smoker always results in dirty smoke for a bit. What I started doing with my Akorn is to get a small amount of charcoal fully lit on the main charcoal grate, and use it to heat up (but not light) a large supply of charcoal on a higher grate for an hour or so. Once smoke is clean I dump the upper grate into the lower, and set dampers to control air supply (or use FireBoard drive). It quickly gets to temp, and holds for up to ~12ish hours of good smoke on the Akorn. Thing is, its a tiny work surface, and it was only good, not great smoke flavor. I think I could improve on the smoke flavor by playing around with where I place wood chunks, but its a big pain. The masterbuilt is just so easy to get 7 hours of great clean smoke.
Maybe on the Masterbuilt I could add charcoal like you suggest at the halfway point, though there is still going to be dirty smoke from the cold charcoal.
I'm actually curious what is going on here? I think either there is residual leftover bad smelling outgassing compounds left over from charcoal production, or charcoal absorbs all kinds of stuff when it is cold/cools, and when you heat it all that bad smelling stuff outgasses. If it is the latter, then I wonder how long charcoal that has been lit, and then cools will take to become dirty again? Is it dirty as soon as it cools? Or does it take days/weeks to become dirty again? If it takes a while, then a strategy that might work, is to empty the charcoal leftovers of any previous cooks after the charcoal is cold and save that "conditioned" charcoal for the future in a nice airtight container, and start new cooks with fresh charcoal. Do this every time to build up a supply of "conditioned" charcoal, and then use the conditioned charcoal to refill during cooks. It really is not a lot of extra work if it works. It kinda doesn't work if you only do long low and slow cooks that always require adding charcoal. If you are like me and do a ~3:1 ratio of weeknight grilling to weekend smoking, then it might work well.