WD40 is unpredictable to a degree-- I've found it will work on rattle can paint (at least the cheap stuff you see in the big box stores), but it will damage some types of factory vintage paint too (especially hand pinstriping). It will also create "grease spots" on some vintage paints as well. Then again, I've found certain types of rattle can paint resist WD40. I guess it's hit or miss. I'd avoid that method I guess, just because it can cause some real problems with certain factory paints.