I do a little bit of painting and this is what I recommend. Get some fine steel wool and rub down all the surfaces you will be painting. Ultra fine if it is plastic. Then use some clean, lint free cloths and wipe it all down with some acetone. This will remove any oily residue or dirt. After this you might want to use some latex gloves when handling so you dont get any oil transfer. First prime your metal surfaces with prime and etch. This will ensure good bonding. Let dry for about an hour. If you are concerned with lint or trash, get some sheets of plastic and make a small "paint booth". Save enough to cover your opening after painting. I go an extra step and use a form of electropainting, but you dont have to. When painting your pieces, dont coat too heavy, and with smooth even passes. Start to spray before and stop after your pass. Practice on something first to get the feel of it. Put on a coat, wait about 15min, apply a second, wait 20min, then your final. Get a small #1 brush for touch ups. Spray some paint in the cap, and use that. For the interior I would not use clear coat, it will catch every scratch and nick. I also like a satin finish on the interior, it cleans better, and shows the light from your led's better. At this point , if you are using a UV light, you can use some UV reactive clear. If you want the outside glossy, you can use a clear after it has fully cured. Use some ultra fine steel wool to scuff the surface, clean then apply the clear. Apply the clear a little heavier than the color, and let it set about an hour between coats. It is really important to keep your work area as clean as possible for your clear coats or you will get a bunch of trash in it. If you can heat a room this will be good also. Humidity is your enemy. Pick a nice sunny dry day to do this.
Here is a site that might help too.
http://www.duplicolor.com/index.html If you want some really durable paint, use epoxy based paint, you can get it at most paint stores that sell automotive paint.
Have fun.