(This log details work from July 2014)
With nicer weather than the last time I tried to paint the enclosure, I gave it another try. This time, I was careful to sand off all the paint and start fresh. I also tried adding primer, but I didn't realize we were all out.
I painted two coats of black matte enamel spray paint (same as before), but this time I used two coats of clear gloss enamel hobby spray paint. Last time, I used a different clear coat that wasn't enamel. I also put an extra layer of clear coat on the bottom to prevent scratching.
The finish ended up having a very nice texture. I did miss a small area painting one of the corners black, and I missed one layer of clear coat on part of the lid, but overall I'm pleased with how it turned out. My fingers are crossed that I don't have to repaint it again (or at least for a long time).