I got corolla cvt 2017 se car which i sometimes take up the hill on hiking trips to trail head. My worry is when I driving downhill it drives uncontrollably and requires constant braking. This clearly puts stress on brake pads and I was wondering about avoiding it. I know there is manual gear option in gear box using "S". I however do not know how to use that to avoid uncontrolled speed while going downhill. I tried researching over the internet and couldn't find any proper response.
You are absolutely correct about wearing your brake pads.
You need to downshift.
My car, a 2016 Toyota RAV4 hybrid too has S position even though it has CVT. The S position has 6 simulated gears. You move to the S position laterally from the D position. Then, in the S position, you push the shifter forwards or backwards to upshift and downshift, respectively.
The controls of your car may differ, obviously, so that's why you need to consult the owner's manual.
In a lower gear, there is more engine braking and less need to press the brake pedal.