P-51s had a notice on the instrument panel advising the pilot to lower the seat before jettisoning the canopy - I think the jettison lever is on the right hand side. In general, I think the advice for most WWII fighters was to roll inverted if you had the time and altitude, but otherwise try to go out low and sideways, so hopefully you went under the elevator. Frankly though, in the circumstances of an incident like this, I'm not sure you'd have time to think.
It is good to see that nobody was seriously hurt. Sad to see a warbird written off, but that is less important.