I fill my carboys about one-third full with warm water and add two tablespoons of PBW after an initial jet rinse. Swirl the carboy to mix the PBW and then invert in the sink. The solution covers the krausen ring. There usually isn't anything stuck to the glass below the krausen ring.
A day or two later I tip the carboy up and give it a quick brushing. Dump and then jet rinse with warm water. Inspect under a bright light.
I go light on the PBW so minerals don't precipitate out and stick to the glass. To prevent stressing the glass I never hit it with cold water or hot water. The carboy is also always cushioned to prevent cracking, immediately or later when it is full of beer.