I'm not certain that there was much, if any at all, training at the twin engined planes. One of semi-official procedures was for a novice pilot to seat, or rather kneel, just behind the pilot, so he would get as much as feel about the plane . Plenty of the plane it was, so were previously mentioned fighters with R-2800. What's the saying, there is no such thing as a free lunch - it took size to accommodate what was necessary to do get the job done.
Now that we speak about German footage, there is a nice part where P-38, while flying tree top, simply out-turns the pursuer. P-38's pilot started a roll, turns in and starts climb, all in few seconds, so German losses him.