Check these out.
http://www.meguiarsonline.com/forums/showthread.php?17443-Not-very-happy-with-ScratchX
Only work about 5 to 6 inches of the scratch at a time, first see if you can make a small section of it go away, then cookie-cutter your results over the rest of the scratch.
Not sure how deep this scratch is, but we've seen similar scratches that look as thought they were put in with a razor blade, so they are thin, but deep, in these case you cannot remove them at all.
When applying to remove a 5-6 inch section, use about a teaspoon of product, in your situation, better to use too much than too little. Spread the product out over the section your working, and move your applicator pad across the scratch, not in line with it, actually at an angel to it is a good practice. You can even rub in two different angles with repeated applications.
Rub using around 8 to 15 pounds of pressure to the pad and move you hand in a back and forth direction quickly, like you're a machine.
"Be the pad"
as Chevy Chase would say...
Apply until what starts out to be an opaque/whitish film turns to an oily looking film then remove. Don't pay any attention to the directions that direct you to let the product dry, these are wrong. See this article,
Then wipe off the residue and repeat until you done this at least 3 times. After each application and removal, inspect to see if you notice any improvement. If with each application it gets harder to see where you applied the product then continue until it's gone you feel to any further could go through the clear coat.
If you see absolutely no improvement after 3 applications, then the scratch is either very deep and you're actually improving it, (this means you're remove the paint surround the scratch but because the scratch is so deep you cannot and will not see any improvement).
Or
The paint is so hard that you cannot remove small particles of the paint by hand.
If you were nearby, we would love to have a go at it just because we love a challenge.