Sniper dude is right, the vinyl stuff is really good but it isn't paint. If all of the case is plastic then you could use the vinyl pigment myself and it would probably look OK, but it will cost you though as the area you have to cover is large. (This stuff is better for recolouring DVD drives and the like). I think that a standard spray painting will probably look terrible unless you are a professional.
What do you mean when you say you have stripped all of the plastic off BTW?
Already said before: Three tins of paint or whatever is too expensive, just buy a new case. If you really really don't want a new case try the black vinyl, but I don't think that the look of that case is ever going to be significantly better.