High risk technique, wet it, stretch it, and dry it out. Less risk, DBFs try to re-tension it and punch some skirt holes and lace it.
Next time I can recommend treating the saddle with Nik Wax Aqueous wax a few times. I've done my saddle and it's effectively waterproof now, without any softening, as it doesn't contain anything animal. Even better, you can apply it when the saddle is already wet, it actually works better that way.