I would advise against acetone for the simple fact that it evaporates very quickly. With the buildup you are describing, it will not have time to penetrate before it evaporates. Go to the store and buy small quantities of different types of paint thinners (ie naptha, xylene, paint thinner, minneral spirits, etc.) and test to see which one cuts through the glue. After you figure out which one works, stop by a Sherwin Williams store and buy in bulk.
The other option that has not been discussed is media blasting. I know they sell different types of media that won't harm the aluminum but may take the glue off. Just a thought...