To get the movement right, do it yourself first, in front of a mirror. No wait. Make sure no-one is watchng you before you do this, so you don't look stupid.
Pull out your fake gun. Look at your arm position(s). Draw the same position on your char. Then draw a frame about half-way between these two 'extremes' (the one with the arm down and the one holding the gun.
A good way to do this is to start off drawing the arms as sticks in the position you want them. One the movement is right, then you can build up the rest of the arm around it.
Keep doing the inbetweens in this fashion & you should eventually come to a satisfactory, fluid movement.
Pull out your fake gun. Look at your arm position(s). Draw the same position on your char. Then draw a frame about half-way between these two 'extremes' (the one with the arm down and the one holding the gun.
A good way to do this is to start off drawing the arms as sticks in the position you want them. One the movement is right, then you can build up the rest of the arm around it.
Keep doing the inbetweens in this fashion & you should eventually come to a satisfactory, fluid movement.