I have one of those tube thingies but seldom use it. Both of my pellet machines will impart nice smokiness without add-ons. When I slow cook I've modified all my recipes to change the temp and timing to include a low temp "smoke bath" to start the cook. For instance, when I do ribs I start them fresh out of the fridge (trimmed and rubbed, though) at 180 for an hour. I do similar things with most other meats. Nice smoke impact.
Hub