Iv always thought "cleaning" rust away required sanding.
That's not required, but might be an effective and cheap way to remove it on a larger surface which is easily accessible and can be or even possibly should be flattened anyway. However, that's absolutely not the case with rock chips, which are tiny spots and are craters in the surrounding paint, which you should try to leave as much untouched as possible. Otherwise you will just make the chip larger, which in turn will need more paint to get filled, more sanding to get perfectly flattened and blended, and if there will be any difference between the original and the touch up paint (which always will be in the case of metallic paints, even if the color match is perfect, which again, won't be if your paint is older than a few years) will make the corrected area easier to spot.
So, with rock chips the best solution is to use something that dissolves rust, but doesn't touch neither paint, nor the in-tact metal below the rust. Iron oxide removers like Iron X do exactly that. You might want to use a qtip to agitate the remover in the chip craters though, otherwise you'll need a lot of repeat applications until it can remove all the rust on its own.
Is Iron X and 3000 grit enough to "clean" and neutralize the rust before primer and paint?
Iron X does not "neutralize" the rust, but dissolves it and carries it away. Or more precisely: let's a wipe or a rinse with water carry it away. Sandpaper is not needed for rust removal from rock chips, and is actually in my opinion the worst way to remove them, for the reasons explained above.
