Saltydog, 1337, Mike V, Cbreeze, SFProps, Snowy, Tweety1, thanks to all you fellas for your responses...sounds like I have lots of ways to go, but definitely mix paint outside the resevoir, then pour it in.
Mike V, which retail stores sell those mixing cups?
If there's not one close by, I just might go the film canister route, since those seem "bendable" to pour into the small paint reservoir on the HP-C