I use acrylicds 99.9% of the time, and to help with adhesion to the PE parts, I give the part a nice wipe over with some Iso, then a light sanding with a fine grit sandpaper, just enough to lightly scratch the surface.
Work in a circular motion if you can, this helps to hide the scratching.
Then another wipe over with Iso, and she's good to go to the paint booth.
Just remember to prepare things like PE flaps etc off the model.
It's easier for a start, and allows you to paint the part in all it's nooks and crannies before attaching to the model.