Back in the day (pre 1940’s) you had two main top coats for furniture: Shellac or Laquer. Both are solutions which means they are things suspended in solvents. The solvent keeps it liquid so you can apply then evaporates away, leaving behind the thing that protects the piece. That means in you re introduce the solvent, the finish will dissolve again and turn back into a liquid solution. When it’s liquid you then push it around, wipe it off or both depending on how new you want the outcome to loo