On the steam engines, when they are listed for smoke and sounds, how is the smokestack different? I assume it is lined or insulated and deeper. Is there a small coil of material or pellet that can be lit and dropped in? Iv'e seen the "smoke oil" mentioned, how does it work? How hard is it to convert to a smoker and I just realized that when I see steam engines on layouts, I don't see any smoke. Why is that?-------John R