I think that paint would work well without too much prep work.
With any paint, it's best to try a sample spot on a place you won't see, the backside of the motherboard tray or something of the sort. It seems like it should go on the case easily, you might need to slightly scuff the surface with a finer ~200-~300 grit sandpaper for the more glossy surfaces.
Also, the darker the surface you are trying to paint, the more coats it will take to fully cover well. It will take time, but more coats will look so much better than one thick coat, especially on the glossy plastic surfaces. A small foam sanding pad can help you rough up the more curved and irregular shaped parts. It's probably safest if you remove heatsinks and other large...