I've done something similar a long time ago; using raw read commands, reversing the descrambler output, and then statistical accumulation on the actual bitstream. By showing the output in real-time on a bad-sector you can actually see the signal appearing above the noise.

It's strange to see no mention of cleaning the drives themselves, although maybe it was implicit --- if you have a pile of old drives sitting around, chances are they're not going to be perfectly clean. A tiny bit of dirt on the lens can have a huge effect on the read signal, especially on a marginal disc.

Related article from 18 years ago: https://news.ycombinator.com/item?id=21242273