I do what many do and that is to stuff the spout with green grasses and leave that there.
Then when I pack up I just put the smoker in my approx 12 gallon galvanized bucket that has all my smoker fuel and lighter in it and put the top on. Probably some minor risk of a smoldering fire, but the lid is pretty tight and any residual embers in the smoker after stoppering up the spout with grass likely is starved for oxygen.
I prefer this to putting the stopped up smoker in the back of the truck bed as it may tumble around and then really cause problems.
After I put it in my covered steel bucket I could probably even put it in the back of the cab as it doesn't smoke anymore at this point, but nice to not have that residual smoke smell in the cab.