Cleaning a Masterbuilt electric cold smoker attachment

I've had some really good input from folks on this board when it comes to my Masterbuilt electric smoker and the side smoker/cold smoker attachment. So, I'm turning to y'all again.

I need to clean the chip holder of he side smoker. I don't know if it is creosote or aerosolized fat, but the inside of the chip stack has gotten coated with a dark, sticky residue, to the point that the chips will stick to it and not fall down to the heating element as the chips below burn up.

I'm thinking i need a wire brush of some kind, but the stack is too narrow for a regular wire grill brush. I'm thinking maybe a small round brush, maybe even something that would attach to a drill. soak it in a water/cider vinegar mixture and run it up and down each wall while the drill spins it.

Thoughts or other suggestions from the folks who own one?