I've got an old demijohn I hardly ever use. I put a few litres of sanitiser in it and a bung with two holes. One has the tubing from the fermenter, the other starts off with an airlock. When I'm down to about 10 SG points left I'll replace the airlock with a mylar balloon. I'll then crash down to about 4C for a few days.
That said, the only reason I crash these days is to experiment with cold dry hopping. I used to crash when I was dry hopping loose to stop the hop debris blocking up the keg posts and the transfer. It never really worked well enough and I've moved back to dry hopping in bags. So if I was hopping at normal temps I wouldn't bother with the crash and just bottle/transfer to the keg.
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