You're kidding, right? One of the first things any manual tranny driver -should- learn is how to hold a car steady on an incline using JUST the clutch and accelerator. Once they master that skill, they need to practice releasing the brake pedal and THEN holding the car steady on a hill using just the clutch and accelerator, without rolling backward. For learning purposes ONLY, the hand brake should be used until you get a feel for where your clutch start to "grab" and how much "gas" to give the engine so it doesn't die on you.
Now there are a lot of incompetent manual tranny drivers who can NOT hold a car steady on a hill using just the clutch and accelerator pedal. There are also a lot of incompetent manual tranny drivers who can not release the brake pedal on a hill (and not use a hand brake) without rolling backwards.
But any competent DRIVER knows that two feet (at most) is all that is needed to hold a car steady on a hill without using any brake (hand or foot), regardless of type of transmission. And FWIW, I've seen some slushboxes that roll backward on hills, also. So holding a car steady on a hill without using a brake is a skill that ANY driver should have, not necessarily just MANUAL tranny drivers. -Dave