any + experience with CD disc modification ?

FWIW - I've blind tested the following tweaks with several friends and my spouse: Herbies Black Dots, freezing disks, Walker Ultra Vivid, Olde English spray polish. All listeners have noticed a difference between treated and untreated disks of the same recordings; differences we all consider positive. i.e. the listeners invariably liked the tweaked disks as do I. Incidently, I prefer the Olde English to the Walker for treating the disks. And, it's a lot cheaper - about $4 at Ace Hardware - vs $75. for the Walker Ultra Vivid.
I've also tried the green edge treatment and none of us could hear a difference.

An inexpensive alternative to Stoplight CD markers is to purchase a water-based acrylic marking pen at an art supply store in your choice of colors for about $4.00. Same thing, lots cheaper.