i sand the boxes smooth starting with 150 grit paper to remove any seams left over from casting, then work my way down to (or up to depending on how you want to look at it) 440 grit, once you get to 440 grit they are nice and smoothand start to take on a shine (partially polished) i wash them down with ronsonal zippo fluid, removes any grease, or oils the metal happend to pick up from my fingers if i forgot to wash them
then i lay on a really thin layer of chevy orange paint just enough to mist coat the whole box, i do this because orange seems to be cheaper than primer grey lol, i do this on all the boxes regardless of color, it helps make sure i get a uniform coating, orange shows where i missed and through the next layer of paint, i let that sit for about an hour next to the wood stove (it gets mighty warm over there helps cure the thin layer fast), then i put the first color coat on a fairly heavy coat almost to powder coated thickness, and throw the box in my handy toaster oven on 125 for 2 hours, bakes the paint hard (hopefully i don't typically abbuse my boxes so their durability is questionable in the hands of a gigin musician) after which you get something along the lines of this picture, which gets a second heavy coat, i don't bake this one, i haven't found a reason toit's just a coat to make sure the color is uniform