I agree with garry, there is a lot of info on polishing here on the forums. But to help clear things up a bit for you...Walbernize is intended more as a protectant for clear coat-type finishes, much like a wax for your car. Nuvite is a series of compounds used for removal of oxidation.
For polishing a vintage trailer, there are many methods, however the most widely subscrided to method is the Nuvite/compounding/cyclo-polishing techniques as found on the PerfectPolish.com
Good luck in whatever you decide to do!