How can i remove these white marks in the side rear windows?

i have readed that taking the winow from the car and wet sanding the black part until the white is gone and than respray with black primer, can anyone confirm this or has better working methods?

i have readed that taking the winow from the car and wet sanding the black part until the white is gone and than respray with black primer, can anyone confirm this or has better working methods?