WD-40 is the answer. I works great, but then you do have to wash the surface well afterwards and re-wax that area.

 

I've used a WD-40 soaked rag to remove bugs and tar from my vehicles. Use it before you wash it (so you can wash it off with the rest of the dirt) and then wax it. It also works good to remove wax residue from the plastic bed rails, tailgate handle, plastic bumper guards, and mirror support on door. Take a wet rag (water) to wipe up any you got on the paint.

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1998 F-150 XLT 4x4, Regular Cab, Short-Bed, 4.6L V-8, 5-Speed, 3.55 Rear Gears, Dark Toreador Red