thksYou can find the PL-21 users manuals for several aircraft via some clever Google searches. I don't believe I've seen one for a 250, but the ones that are available are close enough to get you familiar.
There is also a PL-21 desktop trainer program that you can get through some of the torrent sites -- it is for a Beech Premier, but the basic mechanization is the same as on the King Air.