You can make it a little quicker with a heat gun. Like 15 bucks at harbor freight. And like doc said...WD40 is the bomb. For stickier stuff like big boat side decals, use stuff called goo gone. Spray it on, let it sit 5 minutes then wipe the glue off. Finally, finish off the area with a bit of rubbing alcohol on a towel.
Then wax and buff the area.