I believe it's the Novus 3 that is the heavy scratch remover compound, but it depends on the depth of the scratch whether it'll work or not. You might have to wet sand deep gouges / scrapes with fine grit pads and then switch to the Novus 3, then work downwards to Novus 2 and then finish with the Novus 1 / polish compound. In some cases for REALLY deep scratches, it's better to just fill the scratch with clear filler material and live with it rather than sanding a portion of the tank down to remove it, which would weaken the panel in that area.
The smaller bottles of Novus at TAP are about $3 or $4 each, so you can get the entire set for about $15 plus maybe another $5 to $10 for polishing / buffing pads. Those kits linked earlier would probably work just as well, but they seem to be for large area or entire panels which would be spending way more money than necessary if you just wanted to fix a few individual scratched areas.
