I have 250' of Aristo-Craft track in the yard now and has been for 5 years. I use a drywall sanding pole with a 2" x 4" x 8" long block of wood screwed to it & 4 strips of velcro, I then attach a green 3M Scotch Brite cleaning pad to the velcro strips (easy to change the pad) and in 20 min. it is nice clean & brite.
The track is to expensive to use any kind of sanding paper no matter what grit you use.
the 3M Scotch Brite does not remove brass just the tarnish and quickly.
By the way a box last about 2 years