ouch!
so using your groin to stop a moving vehicle actually works in practice, but isn't advisable
I did a similar thing once, but with the door shut and window down, I thought that as it rolled out the garage I could just reach in and pull the handbrake up... not a chance could I reach it diving through the window
car rolled down drive and came to a stop blocking the road (luckily a cul-de-sac with no-one around to bump into, or witness it )