How to soften the Vinyl on seats and door trims.

[Ex Army FC 217]

Does anyone know a method or product etc that will soften the Vinyl on my FC Army sedan.
The FC 217 has its original seats and trim in good condition for its age but im too scared to sit in the car for fear of ripping the seats as they seem very hard.
Any ideas how to soften the Vinyl??
I dont care how long the process takes to soften as long as i can save the interior because its one of only two Army staff cars known to survive and probably the only 1958 FC 217 Army Staff car left in existence with its original brown interior and exterior paint.
As many people would be aware the other known Army car was fully restored by Ken.
Im also trying to get the rust stains and spots off the paint if anyone has a safe method to use that wont take off too much paint .
Thank you in advance.