What I would do is get a long breaker bar or a breaker bar with a pipe and use the weight of the car to torque that sucker down, here's how.

Put your bolt in with the socket and breaker bar on it. Now hopefully the parking lot is pretty smooth, because you're going to put the car in gear, and push the car so that the crank is being turned and will try to turn the breaker bar along with it, which will be on the ground and trying to lift the car.

If the parking lot isn't smooth, then yeah, set the parking brake tight, put the car in a low gear, and get as much torque on it as you can manage.

Either way, if you're worried that you can't get the proper torque on it for the drive home, put a dab of locktite on the bolt and then redo it when you get home.