If I want to pass, I just force a downshift with my foot. Sometimes I don't need to force a downshift 'cause I don't necessarily need to increase my speed so much.
I turn it off for downhill mountains, helps save the brakes a bit. I've never had my car smelling to overheated brakes before.
If the uphill is steep enough, I might turn it off as well, since there might not be enough power in 4th gear to maintain my speed.