While I am no automotive expert, I have lived on or near mountains (well, a ridge) since childhood and can tell you that brake wear can result even from gradual braking.
Yes, rapid stops will wear down your brakes more quickly than gradual braking, but it is important to note that staying on the brake pedal for too long (riding the brakes) on a steady downhill will also eat your brakes for breakfast (brakefast?). I hate getting stuck behind some driver with no experience on the main road up Signal Mountain who rides their brakes constantly; I do not love the smell of burning brakes in the morning (or any other time of day).
The trick to helping your brakes live a long time is to ease into the brakes until you get the stopping power that you want and then ease off and repeat. I frequently pump the brakes 2-3 times before finally leaving my foot on the pedal to come to a complete stop. Brake early and gradually. It helps to know when you need to stop, so obviously this trick won't work on roads with which you are unfamiliar and/or in emergency situations where quick stops are necessary.
And yes, engine braking can work quite well, though I have never bothered doing so on my vehicles.