Well,, there are "Hot-Wax" type products that you can spray on with your pressure washer.. This is basically the same wax used at automatic car washes... Will it make it shiny again.. Can't say.
Is it as good as say Simonize... NO. in fact very little is.
That said there are several products that are nearly as good as Simonize, but a lot less work
If your rig is fiberglass.... Check out products made for boats, which are often painted fiberglass. I can not recall the name less I'm looking at the shelf at the auto store but it begins with "M".. the one that comes to mind Meguiers or something like that.. Hold on Meguiar (At least that is what Google found)
Now I have never used this stuff
Shampoo & Conditioner and in fact never heard of it till I went searching for Meguiar
http://www.meguiars.com/estore/product_list.cfm is the company products page for Meguiar.
NOTE: this is only one line of products.. One I see advertised often.. I have used some of their products but can not say that they are better than other products I've used.
But waxing it, the old fashion way.. That is still the best.
Note if it's lost it's luster.. There are multi-step restoration products.. I think that line above has some.. That will work better than a straight wax as a rule.
Ther are also single step products such as Nu-Finish, that claim to do the job
Again, I have not been all that impressed... but they do work.