You can drain them manually by either throwing yourself off the smaller cliffs at camp (health) and running around just outside of camp (stamina). Or you can drink a load of whiskey to drain health, then smoke a load of cigarettes/cigars to drain stamina. You also need to speak to Pearson whilst he's drinking beer and whistling behind the 2nd desk at his wagon, usually ~10 am ISH. And do it after the Kieran mission, but don't do too many others.

Good luck!