Had to address this on my own Christmas layout and because of the large number of newcomers and folks just setting up Christmas trains, I unburied it from another thread... Because THE TREE makes for about an 8' tunnel that's a bear to keep the track clean in, I brought back an old favorite for track cleaning. Using Masonite, I cut myself pads 1 3/8" x 2 1/2" in size. I laid out a center line at 11/16" lengthwise and cross lines at 3/8", then epoxied two 1 1/4" drywall nails centered on the cross lines. While hardening, I drilled two 1/8" holes centered into the bottom of my car 1 3/4" apart. I then set the pad lengthwise on the rails, placed the car over the nails. That's it, there are no fasteners as the pad needs to freely travel up and down. Leave it in your regular consist and you'll never have a problem with dirty rails or wheels thru the holiday. It's also easily modified for Thomas' Clarabelle coach by shortening your measurements. The second pic shows just how much dirt "clean" track gives up after 20 laps.