This is not a real technical briefing, but the engine you mention was originally an APU, then they started building airplanes around them, it is a single spool direct drive engine, where when one turns the propeller, all the bits inside move.
Because everything moves at once, they go through a lot of trouble to relieve the drag for starting, like venting the oil pump initially and by the pilot locking the propellers at a certain minimum drag position with the help of centrifugal pins on the previous engine shutdown.
On late model applications, a computer handles everything after reaching 10% provided batteries / GPU isn't an issue.
If you release the start button prior to 10%, the engine will just spin down to a stop.
As I mentioned, the props are locked into a fixed position for starting, so prior to taxiing, you will have to bring each thrust lever towards reverse slightly to relieve the pressure on the pin holding the props, an indication of this is a small spike on the oil pressure.
Cheers, D.L.