By any chance did you simply wipe the wax/grease remove over the part with a cloth, instead of spraying it on?
I have tried paint thinner for part cleaning, and the results were awful. It was as if the paint thinner left oil behind that showed up during the cure. If you cleaned the part with thinner, then wiped it down with wax/grease remover, it wouldn't clean the paint thinner residue out of the pores and you'd probably see something like what your picture shows.
I stopped using paint thinner because I could never be sure I had gotten it completely flushed out of the pores of the metal.
Not sure if that's the problem, just a wild guess
Steve