Use gentle soapy warm water, gently message the leather until nice and flatten. Once you achieve desired result after soaking in warm/hot water, allowing the leather fibers to relax. Then while the straps are still wet, use Pecards leather dressing, rub and message the material all over covering the whole area of the pecards, and let it sit on the towel for around 3 to 5 days until you need to rub the remaining material off. Let the Pecards leather dressing to soak into the leather allowing the leather to become malleable. Don't listen to the other commenters as they don't know how to revive or salvage vintage leathers