The following information on two handed shooting shooting comes from Section 50 of Shooting by J. Henry FitzGerald. Shooting is also available to purchase in print.
After running a short distance the officer may find as he stops to shoot that he is trembling badly and cannot take steady aim. In that case place the hand holding the revolver firmly in the palm of the other hand, the first finger of the outside hand to be just under the trigger guard and the thumb over the thumb of the hand holding the revolver. Use pressure enough to steady the revolver and if inside of fifteen yards use double action; if at a longer range and time permits cock the hammer with the thumb of the outside hand and shoot single action. Very accurate shooting may be done in this manner and the officer will find that he can shoot faster and with more accuracy after a run if the arm is held in this manner.
In this shooting if the revolver is held in the right hand and both placed in the left, the left foot should be placed ahead of the right and slightly to the left or nearly the position of the feet for left-hand shooting. If arm is held first in the left hand the position would be reversed and right foot would be ahead of the left. A little practice using both hands will convince the officer of the value of two handed shooting.