I just resurfaced my flywheel...what I did: I stuck a flathead between the bottom (or anywhere around the tranny) of the tranny and the flywheel and basically held the flathead up so it can catch a piece (little teeth of the flywheel) so it would stop moving and with my other hand I loosened the bolts.
I use a wrench or socket on the crank pulley bolt and use the floor to hold it if the engine is out of the car. I've never had a problem doing it that way although sometimes I have to sit on the engine if the bolts are really on there. If the engine is still in the car you can do the same thing b/c it will start to hit part of the car and that will hold it.
Have someone hold the crank pulley bolt to keep it from turning