I know this reply is late, but I just got a spa and am searching for info on it and ran across your post. I previously saw a post of this site that talks about how theis product "Leisure Time Spa Gloss" has kept a member's spa looking like new for over 10 years. I would think it could add a shine to yours like a good auto wax- but it sounds like it would definately seal if well for you to prevent further damage.
Here is one online store that carries it- but lots do.
Good luck!
~Jana
http://www.hottubworks.com/cgi-bin/comm ... on&key=LTP