HI
Having worked in the Motor Car Paint industry for sometime, (a long time ago)
i can tell you that,
Normal Spray paint (aerosol) is generally CELLULOSED based, It will not hurt you housing at all but then again it will not really stick to it, it will appear to but will fall off after a short time.
you will more than likey have to address the area with an etching based primer firstly to give a good STICK to the metal, then apply a coat of 2 pack paint if you can get your hands on some.
the best thing to do is to pop over to you local car sprayer and ask him if could have the left overs from his WHITE jobs.
Now 2 pack paint has a Half life, once mixed with its hardener it will only last a few hours then it hardens off rapidly.
so you need to stick around there or ask him/her to give you a call when they have mixed some up
and TAKE BEER for them as a gift of thanks.
you might find that most housings our what we call POWDER COATED.
regards
Craig