8x10 instant film is coming back via Impossible.

Recovering the negatives on Fuji FP-100C is as simple as:
1) let the negative dry after peeling the print from it
2) using common household bleach remove the black ink layer from the back of the negative, careful not to touch the emulsion side of it as that will take all of the emulsion right off of it.
3) dry the negative again to let all bleach evaporate and keep from transferring to the other side.
4) rinse the dried goop off the emulsion side, use cold water to keep the emulsion in tact. If after a few minutes of rinsing you still have stubborn area gently use your fingers to rub the goop away.
5) dry

Bleaching without damaging the other side is the tricky part. Some tape it down to keep it away from the other side. Some use a bleach foam product. I just lay the neg. on 4 or 5 layers of paper towel and using another paper towel work from the center to the outer edge, switching paper towels to lay the neg. on when needed. It isn't an instant process.