The regular DupliColor Engine Enamel completely dissolves when sprayed with brake cleaner, carb cleaner, and Gun Scrubber. You don't even have to scrub it, just spray it on and the finish literally melts off. I learned that the hard way myself.
The regular DupliColor engine enamel is different from the bake on high temp stuff. I've never tried the bake on stuff, and I don't know if it melts with brake cleaner or not.