I was doing a bit more research after my initial post yesterday. It seems like Testors, from what I found, sort of used their "stains" and "wash" terms interchangeably. Either way, one is enamel and the other is acrylic. Since I work with enamel paints, I might pick up some of the Testors acrylic wash. I'm not sure if my local Hobby Lobby carries them but I know the Michael's down the street does.
Mississippi, thanks for the heads-up about the black wash!
Eric