Final cleanup with a little bit of acetone on a rag

Depending on what is under the skin Acetone might not be a good idea.
A less agressive solvent, such as Xylene, will get the goo off with
less chance of disolving any foam.

Also the autobody industry has some nifty little rubber discs for a
drill that will peal off these kinds of stickers and leave the paint
finish undamaged.
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Leon McAtee