I just did this over the weekend. What I used was Dollar store oven cleaner. This stuff is a nasty chemical so if you do use it use it outside in a well ventilated area, and only let it soak for a few minutes. Then I used a power washer to spray off most of the eaten spray paint. What it left was nice and shiney original paint. Other have used acetone and scrub pads plus some elbow grease. Which is what I'll use to get the remainder off.