I've used acetone a few times, sucessful every time. If the parts are in the fuse, try using a brush to soak it on with. But be careful balsa absorbs stuff like a sponge. I don't think that acetone leaves a residue, someone will correct me if I'm wrong. I think its just evaporates, and fairly quickly too. I had to use it in a "confined place" once on my 1903 Wright Flyer. I had to brush it on a few times to the area I needed seperated, but it worked w/o disturbing any other bond nearby. Also be patient, but you do have to "work it" b4 the acetone evaporates.
Joe