How do I get hardened glue off celluloid?

[Shaun_of_the_red]

Yeah so I glued some cracks in the plastic shell of my accordion back together, clamped them, and let them sit overnight. I tried to wipe away as much of the glue as possible when I first clamped them, but couldn’t avoid some smearage. I’ve been warned against using acetone but alcohol isn’t doing anything—well, it is making me care less the more I drink it—but it’s not removing the glue stains. Help please! I want these repairs to be as invisible as possible!

 

[colinm]

Rub it down with a polishing kit and finish off with the finest compound.

 

[Dingo40]

I want these repairs to be as invisible as possible!

As colinm said (above), once it's hardened, polish it out using ever finer cutting compound.
Like duco repairs to a motor car.