It really matters whether the scratches are superficial or not. By that, I mean whether the scratches are on the surface of the clear plastic layer, halfway through it, or deep and into the actual metallic material upon which the pits and lands are etched. (If that's the case, no amount of restoration you do will help)
If they're superficial, then your goal is to simply make it so that the CD reader's optics can read these etchings unobstructed. This usually means removing a small layer of the plastic in order to remove the scratches (this is what your cd restoration kits do in general), but this presents a problem because the thickness of the plastic actually matters due to the preciseness needed for the laser optics being reflected from the metallic layer, and the path that laser will be reflected, taking into account the distance between the reflective surface and the density of the plastic layer.
What that means is if you remove too much plastic, the laser reflection's path will change due to a change in density, so it will not be picked up in the correct position by the optical receiver that encodes the digital signal.
Thus, you can only take so much surface layer off before you're making things worse.
As such, CD restoration kits are generally only suitable for relatively light scratches.
Secondly, they are designed to also polish the surface after removing the very small layer containing the scratches as to not create more obstruction.
You can follow this line of logic to its natural conclusion that any sort of addition of obstruction (putting toothpaste on the CD) is working counter to the goal. "Filling the cracks", as it were, is not doing anything for the optics in terms of making the obstructions go away. Indeed, it can be assumed that people who have reported success with such methods have likely, and simply, rubbed away the scratches themselves via fine abrasion alone, resulting in a faulty correlation.
This can be observed via the fact that heavy scratches will almost invariably not produce the results you may have heard about, simply because a lot more abrasion is needed.
I say all that to say, you need to gauge the severity of the obstructions then determine whether it is feasible to go the CD restoration abrasion route or some other method. If you think it's your best shot, try it. Just be careful and stage your efforts between tests, so you don't bring yourself to the point of no return with nothing to show for your efforts.
There may be other products on the market that attempt to settle into scratches and harden, then require a minimal amount of abrasion, but do be aware that such a substance will need to provide the same amount of density as the surrounding material, so whether that is out there or not, you may be paying more than it's worth in the long run.
Hope that helps.
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