This liquid lens scratch removal kit gets thumbs down from virtually everyone who commented. Here's a discussion of what worked (and didn't) for these folks.

As a wearer of expensive (aren't they all) polycarb, photochromic, AR/UV coated progressives, I've wondered about this myself. I first thought a trip to the optometrist for a "repolish/recoat" for a reasonable charge might be possible. But was told (true or not, who's to say) that it's prohibited because it minutely changes the prescription of the affected lens.