Hi Jonathan,
To leave railroad tracks in the snow you will need a minimum speed as well as edge angle.
Most skis will not carve at slow speeds. And you need sufficient speed to create more edge angle.
I have to disagree with this. RR tracks are a pure edging movement, speed is not required. Slow speed will require very low edge angles, but any ski will carve.
My guess is the “problem” comes from moving to much too quickly in relation to the speed you are going. Edging movement should originate at the feet and ankles. At a slow speed this is all it takes. Up the speed and you start adding in knees, hips, etc. Slow speed equals slow movements of the ankles.
Practice on the flattest place you can still slide on in the fall line. Just use ankles. When you start to get comfortable you can up the difficulty by working across the fall line, working on double fall lines, anything you can run across. For a real challenge try them from a cat-track up the side slope and back to the cat-track.