get the commercial neets foot oil from wallmart. it is actually mostly synthetic. if you work it into the hide it will stink like petroleum for a while but streach it out quite a bit. work it. and it will soften up and be nice. If you want then you can smoke it for both the color and the smell.
other wise It probably wont hurt it to rebrain it. then resmoke it. never tried it with a commercial tanned hide. I would guess that the cell fibers are not open to the brain oils tho and it prob wont do much if any good.
I would go with the commercial synthetic neets foot oil method.
luck