I've been down that road many times, and I don't recommend it.
Conductive coatings all have the same intractable core problem as metal- loaded resins: You just cannot establish and maintain a continuous electrical contact to and among the actual metallic components.
Effective shielding requires that all faces of a box be in contact with each other along every edge, and that all metallic components of the shield be in electrical contact with each other. Almost by definition, metallic particles in paint can't possibly be in contact with each other, because each is surrounded by a layer of the resin that carries them to their eventual destination and bonds them together mechanically. Fiber loaded plastic has a similar problem; the fibers are in contact only in a statistical sense, and are not bonded in any way that could resist corrosion or mechanical strain.
The typical solution that people who haven't blown all their capital on magic bullets use is a plastic box with a thin, tin or nickel plated sheet steel liner. The liner is typically equipped with lanced and/or formed tabs along every edge that establish contact with adjacent faces, at intervals governed by the wavelengths to be shielded. At today's frequencies, the typical gap between such teeth, tabs, whatever, is typically not more than ten millimeters. For an example, just open the case of a recent Mac or PC. Open an older, slower one, and the tabs will be farther apart. Pretty soon, you'll have to solder all the edges.
Ever try to solder paint? Ever try to establish a continuous, reliable electrical contact to a painted surface? Not possible; trust me.
Another point: The 'conductive coatings' salesmen will _never_ mention the price of the stuff, until they've got you completely committed to using it. It costs more than twice as much as the paint that the salesmen use on their yachts.
-Mike-