I would just add that the way MTH smoke units are designed the rope wicking is meant to be looped up between the twin resistors (a design that I believe is unique to MTH). In that position the wicking inevitably gets charred although I have found that the smoke units still produce a greater volume of output than other manufacturers' units.
I have not found that this design allows for the use of some material other than rope wicking, which is available from both MTH and Lionel.
If you are finding that a particular smoke unit "clogs" there might be a problem about the alignment of the smoke unit output, the funnel connected to it and the stack on the body shell. Lack of substantial output from MTH smoke units is a little unusual but they are just as susceptible to charred wicking and insufficient smoke fluid as other units. Aside from that, however, (1) check your DCS settings to be sure you're on "high" smoke output if you want that and (2) bear in mind that a few years back, DCS-equipped diesels went over to a system whereby the smoke output ramps up with RPMs. That certainly fooled me into thinking my newest MTH diesel's smoke unit was faulty. Why they had to mess around with the perfectly satisfactory and simple user settings I dunno but it was billed as being more prototypical.
