Repaint trunk / boot lid

[ShaneHobson]

We call them boots down under. I think the American's call them trunks.
Either way, I'm talking about the lid for the trunk or boot.

My car was completely repainted 2 months ago.

The boot lid has never been right. It looks like a fine spray of oil or silicone has wafted over it just prior to painting. The painter (who has no staff) is certain that's not the cause, but can't explain it.
He's guessing that something is seeping out of the material the lid is made of and ruining the paint.

Anyway, he's going to strip it back and paint it again.

But I promised I would do some research first.

It seems the boot lid is made of plastic or fibreglass.

Has anyone here repainted a boot lid ?
Any tips / advice ?
Does anyone know just what the boot lid is made of ?

Thanks