Jim's Beer Kit

I don't see how it can be accurate on a plastic bucket, surely it needs to be on a completely sealed container to work?

Today I'm doing first brew in a long time, and my 12th all grain brew. It's loosely based on a hopback summer lightning recipe, and is being called The Hangover because that's how I'm feeling right now (still). 5.7kg pale malt 0.3kg crystal 150 50g Challenger 60 min 16g EKG 10 min 16g EKG flame out ...

I'm looking at using cornies for the first time. Is there a good guide on how to strip and clean them?