I removed my clear coat using Citrustrip, aircraft stripper, and a clean-up "wash." I got some spots that might be described as milky spots, but I don't think they were the result of any of the strippers I used. Being that my trailer was a '73, the clear coat was irregularly disintegrating all over the trailer, so I am more inclined to believe that I had spots where there was no clear coat, that had already started oxidizing (perhaps accelerated by a blob of bird crap), and when the rest of the clear coat came off, revealing fairly shiny aluminum underneath, these oxidized spots became very visible.
Eventually I will polish the entire trailer. Something you might try on these milky areas is a bit of that "Diamond Brite" aluminum toolbox polish (you can find it at the big box hardware stores and some autoparts stores). It has a little chemical oxidation remover, and a little bit of abrasive to it.