Just my thoughts?
I note that they mention showing how to do it and what material. But did they show how it turned out?
At the end, they ask about your experience. Those two make me believe they are not actually offering a solution, but just placing an ad in front of the public for folks who are searching for the "magic" answer. I have bought quite a few scratched tanks from folks who never found that answer.
I also sold them with the scratches because I tried all solutions offered and never found the magic.