I've heard a lot of questions about painting trim on VWs lately.
(Mirrors, door handles, etc).  I have done this successfully many times
- the product to use is:  SEM Paint.  You'll probably have to go to an
automotive paint supply specialist to get it.  If they're a good place
they'll know exactly what you're taking about.  You can use this stuff
on interior plastic as well (dashboard, vents, whatever).  I've used it
a lot over the years and have never been disappointed.  It's very good
stuff.  The pros use it as do most auto restorers.

Damian