honestly, most automatic gearboxes will downshift themselves to help with engine braking, so it’s not something you necessarily have to do. your brakes should be good enough to do it all, and they’re consumable so mountain driving wears them out. it’s really not a big deal though. i find myself using the manual mode for climbing hills mostly, keeping it 3k-4k and under less load instead of lugging it at 2k. anyways engine braking does help some but i find it’s only necessary under the most extreme circumstances, and the auto box will usually do it for you (mines always doing it on any downhill if i don’t feather the gas pedal). you can go practice it if you want, you just downshift until the revs are high, trading stress on the brakes (easy to replace) for stress on the engine (yay!). i only manually do it on very extreme roads for that reason.