Below is quoted from Chris Colby's article
When making very big beers I save 10% of the volume of wort in my refrigerator for krausen beer I also reserve some yeast. Once fermentation stops or slows, I aerate the krausen wort thoroughly, add a pinch of yeast nutrient and pitch the retained yeast to the krausen beer. When the krausen beer is fermenting strongly, I add this to my main batch, often with conjunction with racking. This almost always helps with attenuation and makes for a cleaner beer.
My Question
Is he basically saying that he saves some of his wort and yeast then makes a starter. Then when that starter is going strong he pitches it into his slowed down fermenting beer?
