I went to a talk by an ATA pilot a couple of years ago. He said it was not unusual to fly ten different types in one day and that the pilot's notes were whatever the wartime equivalent of a sheet of A4 was, with weights, quantities & limitations on one side and a set of pilot's notes on the other.
Given that he could be going from a Tiger Moth on one flight, to a Stirling on the next, it was quite an achievement.