If file sharpening is necessary, is it necessary to polish with Roto-Finish and when using only Roto-Finish?
The ideal is to file the first time and later to use Roto-Finish.
After filing, there is no need to fine-tune with Roto-Finish.
However, for the competition, especially if the snow is very cold and fine a polishing with Roto-Finish 400 then 800 will improve the glide.
When you have skied for a few days on soft snow that has very little rounded edge, it is not necessary to file. You can then limit yourself to three or four trips with the Roto-Finish 400.
When you've been skiing for a day or two on hard snow, you can sharp with the Twin Roro Concept, which consists of 10 to 12 round trips to the Roto-Finish 200 followed by polishing with the Roto Finish 400.
This polishing will be done either by 6 round trips with the roto-Finish 400 set to a degree less than the Roto-Finish, or without changing the angle (same angle as the Roto-Finish 200) but with a dozen or so back and forth.
If by 12 round trips to the RF200 you have not found the cutting edge, add some back and forth. If it is still not sharp it means that your edge is quite rounded and it is better to make a sharpening file.
In general, if you don’t do frequent sharpening use the file.