by waaytoomuchintothis » Wed Nov 25, 2015 6:59 pm
As a long time woodworker and track builder, I will endorse the above fully. And yes, a liner of some sort is necessary to maintain shape. I use plastic auto body putty spreaders, both to apply and to slip into the slot to maintain the slot shape smooth. I use them to sand the slot, too. Just wrap some 150 grit garnet sandpaper around it and run it back and forth in the slot. Perfect every time. Ya gotta love good old Durham's Rock Hard.