Hi Alan,
I've never had an issue with the DX320 or DX330 on plastics or fiberglass, didn't even know there was a warning. I've never used the DX394 but I'm sure it's the same. I can't say I've ever had my parts loaded up with a static charge either though. Perhaps if it was a drier climate out here it might be an issue, but I've wiped down entire corvette's with DX320 and never had an issue.

Tim,
The reason I use the Tide powder laundry detergent is exactly what you said, it has no oils or perfumes in it that will leave a residue on your parts. The liquid "Pretty smelling" detergents have a perfumed oil in them that will leave a scum on the surface resulting in poor adhesion and problems applying the paint.
I'm sure there are other detergents out there that will work the same. I know that Ivory hand soap (the unscented bar soap) is the same, you could use that in a bucket of water with similar results. The Ivory is the only hand soap I'll use to wash my hands as it doesn't leave any oils behind either which I could transfer to the surface of what I'm painting.

Jeremy