Steam is the only other thing I'm familiar with, but may be a bit unmanagable for larger panels. Unless of course a steam room were available, then the whole panel could be "soaked" and then weighted down to "re-cure." Without that, I'd give your alcohol and/or bucket soaking method a shot. Worst case I've had- one wing panel of my Astro Hog came out warped and nothing I tried was able to straighten it. Ended up throwing it away to build another.