Driving mountains in Prius

Driving from NYC to Glacier-Yellowstone-Big Horn and back this summer, and as a flat lander with a Prius I wanted advice from mountain drivers how to not ruin my car on the descents. I try to use B shift on the few mountains I've driven but holy smokes it sounds like I'm killing the engine! Any advice on driving well above sea level welcome, and if I should do anything beforehand to make sure my car is ready? Thanks!