Not to downplay the Meguiar's M105 Ultra Cut Compound, as I'm sure it works well, but my father was an auto painter by trade, and he gifted me a bottle of 3M Super Duty Rubbing Compound. This stuff has been awesome for removing anything I've thrown it at. Doesn't mar or scratch up the paint, and after using it, with a coat of wax, whatever I've tried it on looks better then new.

Just a thought.