"His hope of survival grows dimmer as the days go by". Imagine you are in a dark and bad situation. You can see a light in the distance, it is hope. It grows dimmer, less bright with time. Hope diminishes with time. You know the drill. You ask, we answer. You know the drill. Pay when you get on the bus. You know the drill, toothpaste on brush, then brush your teeth. You know the drill. Sock first, then shoes. . Drill - is a procedure, a sequence of events, a set of things to do. To drill, is to practice things, usually in sequence. Drill is the word to describe soldiers matching together, in time, doing fancy movements that make elaborate patterns in displays. . To use "drill" for normal day to day things is figurative, as if we had practiced sequences of things. "You know the drill" is simply saying that you know how this should go, should work, what to do. . You know the drill. Ask, wait for a few answers. Then assess the common themes as the probably correct meaning. Enjoy.

To grow dimmer ... literally means that the light is slowing going out / getting dimmer .. In this case it means that his chances of survival are getting less and les by the day. To know the drill means to know what to do next without needing explanation ..probably coming from the military with reference to marching the same steps day in day out until precision marching was as instinctive as breathing ..