I do very much the same as spitten and drummen.
When using the green scotch Brite I am VERY light with it. Basically no pressure and maybe 3 or 4 strokes the entire length of the rail and that's it. I will do this when I put the call away in the off season after using a paper towel to remove all the chalk. I may do it once, no more than twice during the season if it's seeing heavy use. I do not use sand paper on the rails, green scotch Brite and that is it. I do not want to change the profile of the rails what so ever.
If the call has had a lot of use and the underside of the lid is getting shined up and real slick I will use 150 grit sand paper on it. Very lighty with no pressure, following the radius of the lid, run a few strokes the length of the paddle to raise the grain back up. You do not want to take material off, or change the radius. You are just raising the grain.
The tuning screw, in general leave it alone!
If the call is sounding out of tune, or in need of adjustment, you should not have to turn it in or out more than +/- 1/4 turn in either direction. If you do need to adjust the screw, be sure to use the correct bit, so you don't strip the screw at all. The screw will turn HARD with some box woods.
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