Remove a player's friction while holding down a button

I am using the standard assets first person controller and I want to know how to remove friction from the character upon holding down a key.

Essentially I want the player to be able to slide down hills and gain momentum to shoot up another hill or ramp.

I am new to unity so if somebody could help me that would be much appreciated, I will play with your code until I understand how it works.

FPSController is using Character Controller so it doesn’t have physics so there’s really no friction. You should make your own simulation.
If you use the RigidbodyFPSController, it should be easier by setting its physic material on the collider.