Your definitely on the right road with the track matte idea. I don't know that I'd use Fractal Noise for it, but it would work. You might also try the Film Burn effect and use that as a track matte. In either case, especially Film Burn, you may want to use Roughen Edges too.
Or, you could create some nice organic footage to use as the track matte. In this case, it looks like a couple puddles of ink with an absorbent paper or cloth laid on top of it so the ink starts to seep into it.
- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')
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