On long down hill grades I use B mode and set the cruise control. Just remember to shift back to D at the bottom of the grade. Of course the ICE noise from the high rpms will remind you after a short time, should you forget.

I find if I just coast in B, I loose too much speed on all but the steepest grades. I can use the gas pedal to moderate the effect of B, but prefer to set the cruise if traffic is light.

Sometimes in rush hour traffic, I also use B mode while the car is coasting down grades in EV mode (speeds < 18 miles per hour or the ICE starts) and can avoid riding the brakes. I think it is safer as folks behind me see my brake lights when I do have to slow down, instead of seeing them all the way down the grade.