If you're careful with the auto siphon at the beginning,you'll leave that krausen residue behind. As long as it was at a stable FG,you're good to proceed. After using my 6G better bottle on a batch of oaked stout this week,I noticed how easy the BB are to clean out with a couple good rinses! I guess,even though they're PET,they have a smoother surface that releases the crud better than pails & other plastic FV's do?!...makes me wonder how well/easilly the glass carboys clean up?