Old Thrashbarg wrote:What about painting the case black or whatever the most appropriate solid color, then finding a high-res image and getting it printed on vinyl sheeting (like they do for ads on cars and buses and such)? It'd probably be a hell of a lot easier than painting.
This. I can't think of any other way you're going to get the finish you want.
The effect you're going for is a really complicated texture. The "grain" doesn't just go horizontally or vertically, it goes in both directions. You would have to use multiple shades of the same basic color and mask in between each spray, or maybe you could get away with using a 3 dimensional base and just painting over it (but the same problem, the base isn't just in one direction, and in this case you would want it to be uneven). In a nutshell, if all you're using is paint, the effect you're going for is nearly impossible to replicate. At least in my novice opinion.
What you might also want to consider is tracking down some faux wood-grain laminate and laminating the entire case in it. It's not going to look like aged paper, but it would look old, and might be close enough to what you're going for. The seams are going to be a royal pain though. Or you could see if you can't track down some large sheets of brown paper (like the stuff they make bags out of) and hitting it with some fire to singe it. Glue it to the surface and cover it with clear polyurethane. Try that one on a small scale first before you do it to a case though. I have no idea how it would look in practice.