I have some aluminum "people" I need to apply vinyl to at the local school. I want to be sure I clean it properly. I stopped over and tried to clean one with alcohol and check them out. My rag was black, and it did not come clean after several attempts in the small area I tested. Here is a pic...
Stacey, I'm sure the rest of the suggestions would work, but I used to have to apply to raw aluminum all the time & I always
did what you did, wipe it down with denatured alcohol & never had an issue... problem is you will need to wipe it down several times, replacing the towel
every time, until your towel stays almost white.
Edited to add, if I were to use anything else besides denatured alcohol to clean with, I would still do a follow up clean with denatured alcohol and make sure the towel was clean, raw aluminum has a lot of oils.