i have 3 road cases from famous bands. 2 had real old foam and it had to be taken out. i found nuts and bolts imbeded in the foam and i even found a few t-rods and a connecting rod for a dbl pedal. only the connecting rod was 1/2 visable.
whatever solvent i had at the time only melted the form even further, so i took a putty knife and scrap it all out. most of it came out pretty easy but it does gum up the blade. just wear a glove because if the knife gets caught on the wood, i may suddenly break loose and cut you.
after that i did not take them down to wood by sanding (and i didn't have a sander at the time) so i took some bass drum head boxes and cut them to size to use as a inner lining. came out perfect.