I use it exclusively for cleaning my carboys, about 1 scoop then fill the carboy about half full. On the secondaries, I have always been able to completely clean without scrubbing (a good thing since I use plastic BBs). For my primary (usually a glass carboy) I can sometimes, but not always, get it clean without scrubbing. I just fill the jug halfway with the oxyclean solution then tip it upside down in my utility sink partially filled with water. Through magic or physics or something the oxyclean solution stays in the carboy and is able to soak away most, and sometimes all of the krausen krud that rings the top of the carboy.