Without photos it's really a bit difficult to give best advice, but my first reaction would be do not paint it. Try an area wit T-Cut as used on cars and then a good car polish/wax. Purists will advise using specialist GRP cutting and polishing compounds but you will be surprised at how good a finish you can get. My last van had a chalky roof after being stored unprotected or polished outside for 5 years. After a few hours work it was nearly as good as new, not far off a wet look finish.

Colin

For what it's worth, I'd agree with Colin.

The pop-up roof isn't painted from new - the surface finish is a self-coloured (white) gelcoat, and that's the first layer into the mould when the roof is made. The gelcoat layer is considerably thicker than a layer of spray paint, and as such is able to cope with much more remedial cutting and polishing.

You might want to consider getting a dual-action polisher which will speed the job up enormously. I got one a while ago to use on the cars, and it didn't take long to realise just how much elbow grease I'd wasted over the years in polishing and waxing by hand.

A polisher like this will do as good a job as one costing three or four times as much.

Get a small selection of the appropriate Velcro-backed polishing pads, watch some of the many videos on YouTube and you can't go wrong.

I wish I'd got one long ago.

If you do go down that road, the chances are you'll be so chuffed with the results that you'll be looking around for other things to use it on.

A couple of words of caution if you think about using it on the van body though. Firstly - and for obvious reasons - you won't be able to use it on the dimpled finish, and bear in mind - if your van has smooth panels - that the paint is microscopically thin and there's no lacquer coat to protect it like the one on a car.

The roof, though, would be an ideal place to use it.

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On a slightly more serious note. When I did the polishing job on my last van I did have a bit of an accident. I had the van in the garage with a set of steps up the side, just enough space between the garage wall and the van for them. I started the T-cut and polish on the bit immediately in front of me. I did not realise how effective my efforts were until I stretched out to do a bit a little further away, and slid across the now very shiny and slippery polished surface. The ladder moved and I fell down the side of the van, fortunately wedging myself between van and garage wall on the way to earth. Looking back it was a bit of a Laurel and Hardy moment, funny now but not at the time.

Colin