Hi Scarpius,
The meguiars gold class liquid wax isn't suitable for vinyl as it contains solvents which may damage the vinyl. Not sure about WD40, as it's not something we've ever tried.
Personally, we would simply wax the vinyl with a carnauba wax, just the same as we would the rest of the paintwork. In order to get the best results we'd recommend using a pre-wax cleanser such as Lusso Revitalising Creme or Lime Prime Lite which will deep-clean the vinyl and prepare it to bond well with the wax. The wax will then help to acheive that wet, glossy look you're after and will also provide a layer of protection which will help repel the dust and dirt for longer.
In terms of the shampoo - we use Lusso Auto Bathe on all of our Details and also on our own car, simply because we haven't found any better product - it suds up extremely well, the dilution ratio is great and it smells delicious!
Having said that, if you're happy with how gold class works on your car, just keep with it as it is a good product and it does work well!
Hope this helps
Taryn and Jim