I've actually tried nearly every "LCD Scratch Removal" technique under the sun with spare LCDs we've had lying around the shop. Simply put:
Nothing works.
The only real way to come back from a scratched LCD is to replace the LCD. I'd suggest replacing the scratched one with a new one... but keep it around. You may be surprised how many people with broken LCDs are willing to live with a scratched LCD at a discounted price.