I painted the insides of my case black without doing any priming/sanding. It wasnt really a MISTAKE, but it didnt turn out the way I wanted it to. As for sanding, you should go ahead and do it, it'll make everything worthwhile. All I did was several light coats with the black spraypaint, and it came out alright. BUT, I forgot to use a clear coat afterwards, so the paint chipped off in some places (Inside of the drive rails, inside of HD cage) but you cant really notice it. When I buy my new mobo, Im gonig to coat everything in black again, probably might use 2 whole cans, beecause I want it to be nice, even and ver deep black. Then, Imma use a nice clear coat, so it'll look really nice.

Remember, just TAKE YOUR TIME, and everything will go smoothly.