I had really good results with a purple cleaner.
I used Castrol superclean.
Spray it on , wait a couple of minutes, hose it off thoroughly.
Mine was pretty chalky and dull, with a small amount of mildew, and afterwards it was shiny and had good colour to it. (Timor beige)

However.... I would caution you to do the luggage rack first, with it off the van, and then if you like the results, to do the rest.

I would also use a tarp or large plastic sheet to mask of the van as it can cause streaking on the van paintwork.

Be warned though,this stuff is pretty strong. Of course it can be diluted.
It removes oxidised paint quickly.
If left a very long time it can remove paint.
Wisely used, it can save you a lot of hard work.

Good luck,  Steve Cotsford