What do you mean with the glass bottle?
Printable View
I took a wine bottle and removed the label then with the bottle on its side, I rubbed it vigorously up and down the leather in order to flatten out any areas that were cupping.
Would like to see your strop - can you post a picture? Do use linen/felt or scrub leather before going to the treated leather?
Using the bottle is called burnishing. When sanding don't sand to much or you'll turn the surface into suede like the back.
What they said.. x2