Interesting...
I hand start all the time with 1 particular aircraft I fly (no starter)... no big deal if you brief correctly and don't change what you do if you have a second person.. ie. I always start with chocks in even if someone is in the cockpit and take the engine panel off and inspect the Throttle linkage just to be sure something has not vibrated off and disconnected....
To answer the question of what would I do.... lie flat and if you can roll away from the aircraft.