PE Painting

Roughen up the PE with a FINE grade sandpaper.
All you need is a slightly etched surface, not big gouges.

Then give it a quick wash with some Iso to remove oils etc, and your good to paint!!

Just checked the Eduard web site. In an instructional section the author says that you can prepare the parts by soaking them in vinegar for a couple of hours or lightly sanding them with 100 grit sandpaper. He goes on to say that he doesn't do this because he cleans his models before painting, though he doesn't say with what. He doesn't mention priming, nor does he say whether he uses acrylics or enamels. Don't know if that helps or not, but it sounds like a quick cleaning is all the PE needs.

Best prime it, the metal is very smooth and does not hold paint well.
Alternatively you can immerse it in vinegar for a bit, this also roughen the PE.

I was wondering the same thing. I just got a Hasegawa braile scale Tiger I that came with an Eduard PE zimmerit set. The instructions don't say.