Use acetone, or rubbing alcohol on the case. this will improve the paint bond. then sand. then put a very light coat on at first. Then go back through 12-18 hours later and put a thicker coat on that should cover just enough so that there is no original xbox showing. too much paint looks bad. and dont paint too close. then use a clear coat paint (enamel) to protect the paint.

paint usually doesnt make a difference. Its just expensive brand names. Just find a paint that you like and make sure it doesnt flake.