Suprisingly enough, WD-40 has a lot of usages. It doesn’t really harm paint. Used to use it on my old dirt-bike (Metal fenders,tank with no clear-coat) before going out, would prevent scratching when removing the mud/clay, and made it super easy to clean off afterwards.
It also is suprisingly effective at removing grease. But as for paint splatter, I’m doubt it would do anything unless it’s a softer latex based paint, or if it was still fresh.
I’d say claybar at this point.