What's the best way to clean and shine up a Landau / Vinyl Roof ?
The first step to preserve the top is to keep the car garaged. :o)
For the past several years, I've been using Armstrong Vinyl Floor Polish (http://www.armstrong.com/resflram/na/tile/en/us/fc_detail.asp?productId=18.0). I always clean the top well (using a stiff nylon brush and a good cleaner) before applying the polish. The Armstrong product lasts a long time and gives a nice, deep luster without being sticky or running when the car gets rained on.
When I got my '70 Imperial, the vinyl top on it was very
discolored. It looked like Armor All had been sprayed on it repeatedly over the years, leaving it looking a sort of gooey, milky white color, with a little blue peeping out from beneath. I used Castrol Super Clean (CAREFULLY! This product WILL harm the paint on the car!) to get all of the old residue off, and then used the Armstrong Vinyl Floor Polish after the top was totally cleaned. This is the original vinyl top for the car, and it looks fantastic.