I'm not an expert, the only thing I've cold smoked is cheese in my Weber. But here are some ideas anyway. IMO it seems you'd want to start with a very small amount of high quality charcoal lit with a
charcoal chimney. The advantage is it will burn for a period of time and not go out while at the same time create as little heat as possible. When it's lit and grey, have your wood chips or chunks in the firebox, dump the charcoal on top of the wood, place some more wood on top, creating plenty of wood smoke. You might consider wood-infused charcoal such as what Kingsford sells. Next lead the chimney, stack, or exhaust pipe/hose to the smoke chamber but make it as long as possible. The walls should be thin but don't use galvanized. The length of the pipe will allow the ambient air to cool the temp of the pipe and the heat/smoke before it reaches the smoke chamber. So the longer the better. Consider placing the food below the location of the pipe so that it's at the coolest area of the smoke chamber. Consider having the pipe enter up top and exhaust at or near the bottom. Keep the damper on the smoke chamber exhaust no larger than the air intake damper on the firebox. Check the fire box often, refill as needed. Good luck.
