Depending on how nasty this stuff really is a bug & tar remover may or may not get the job done. At least the Meguiar's Gold Class Bug & Tar Remover sprays out in a gel like consistancy and will cling to the area for awhile as it works against the crud.

The WD-40 and mineral spirits ideas are sound as well and may actually work better if this stuff is as nasty as it sounds. Mineral spirits, as mentioned by Imafink2, are perfectly fine - we use it regularly here at the Meguiar's Garage to remove all traces of compound/paint cleaner/polish etc when inspecting a finish after machine buffing - primarily during product development and testing.

You really do want to avoid any heavy scrubbing of the affected areas though so as to avoid scratching.