Purposely set the cutter askew in the mouth and plane diagonally across the board in an overlapping pattern for quick stock removal.
I think others have already covered the sequence of actual steps needed to four-square a board. As for using a metal jack for removing a lot of material...
I have one and use it often. However, you need to identify whether you have a model that is cadmium plated. If so, you need to wash your hands thoroughly after using the plane or wear gloves when you do use it.