Spray the glass with glass cleaner. This will help lubricate the surface so you don’t scratch the glass.
Scrape the frosted glass off with a sharp razor blade. Sharp razor blades are less likely to scratch the glass.
Rinse the blade when it becomes covered in frost paint. Wipe the glass to check your progress. Rewet the glass and continue using as much glass cleaning solution as needed to keep it wet while you are working. Use a new razor blade once the one you are using starts to drag across the surface. This means it has worn out.
Scrub the glass with a piece of superfine steel wool to remove any pieces of frosting left over.
Spray the glass with glass cleaner and wipe it down with a clean cloth.