Well, if you have access to Tamiya "AS" series spray cans, light gray is a good color to use, as long as you don't spray it over a black basecoat to try and pre-shade it (it looks too blue then). You might be limited on the Testors rack, although they have a light aircraft gray on the standard rack that I believe is really the same shade as Camouflage gray on the Model Master bottle rack (and I believe Camo gray is available from MM as a spray color). To me, straight camo gray looks a little too dark and brown, but it is a good color and I've used it for other SF models.
Why not just take the plunge and request an airbrush from Santa this year? When you have one, you wonder how you ever got along without one for so long.