Looking for a device to detect the amount of smoke
There are a number of sensors aimed at air quality monitoring, such as Sharp's      GP2Y1010AU0F with an analogue output depending on the smoke density, or fancier units such as the Sensiron's SPS30 that has internal algorithms to give counts for different particle sizes.
The problem you have with both of these is that they are intended for air quality monitoring, and might saturate with the levels of smoke in a smoker. You may also experience issues with wood resin settling on the optical components and causing long-term drift or failure.
You may have better results with a discrete solution with a phototransistor and LED - although you will still have the settling problem, you can tune this to your smoke density level much more easily.
A further option is to sense the smoke levels capacitively, although I'm not aware of any commercial modules to do this. A quick search turned up a patent (WO2014022525A2) for using this as a smoke alarm, but you may still run into the issues with drift, both from the change in air density and plate spacing as you apply heat and from deposition of material on the capacitor plates.