Did you get the paint problem figured out?
Whenever I'm doing stuff on metal, I'll prime with auto primer (I know lowes has it) that stuff seems to stick to anything. Next I'll do the colors in flat - the flat paints seem to stick to each other better. Then I'll do the clear coat last. Do a clear gloss, and it will make it all gloss. (I've had other things I want to leave flat, so I use an artist's flat clear coat - because regular "flat" gloss seems to come out sort of satin semi-gloss.)
For diffusing those LEDs, you could use a clear piece of plexi, and sand it on one side. Then just four screws or some epoxy should hold it.
This is one crazy banana ->
