This is a photo of my Horizon 202 (not a Perfekt) with label tape on the rails. You can't see the details very well, because it's black label tape in a film chamber. I don't know how to answer the question of where you put it other than "on the film rails," covering basically all of them. I rounded the ends of the label tape so that it wouldn't scratch the film or worse catch on the the film and pull up, jamming everything. However, I stuck it on there 25 years ago and it hasn't come up, although I have not been using the camera every day. If you look at the bottom left, it shows how I rounded the tape end.
The reason I did this was to shift the focus closer than infinity, not for scratches. If the label tape is 0.2mm thick (I forget if this is the actual thickness), then it shifts the focus point to about 4 meters. At apertures smaller than about f/4 or f/5.6, infinity should be within the depth of field.
The curved film path of the Horizon tensions the film against the rails more tightly than in an average camera. If I had to polish the film rails I would try using something like a Scotchbrite pad and doing it by hand. They may be made out of aluminum, like many cameras, not very hard compared to steel.
You can't use typical plumber's Teflon tape in this application. Teflon tape is intended to be gripped between two things, like in a joint. It would just fall off. You could use stick on Teflon sheets or tape, but only if you find stick on Teflon that is 0.1-0.2mm thick.
The reason I did this was to shift the focus closer than infinity, not for scratches. If the label tape is 0.2mm thick (I forget if this is the actual thickness), then it shifts the focus point to about 4 meters. At apertures smaller than about f/4 or f/5.6, infinity should be within the depth of field.
The curved film path of the Horizon tensions the film against the rails more tightly than in an average camera. If I had to polish the film rails I would try using something like a Scotchbrite pad and doing it by hand. They may be made out of aluminum, like many cameras, not very hard compared to steel.
You can't use typical plumber's Teflon tape in this application. Teflon tape is intended to be gripped between two things, like in a joint. It would just fall off. You could use stick on Teflon sheets or tape, but only if you find stick on Teflon that is 0.1-0.2mm thick.