As with everything this doesnt come easy. Field shooting with any hunting handgun has to be learned and practiced. I have drills that I do every time I take my guns to the range and sometimes while watching TV. THESE ARE TO BE DONE WITH AN EMPTY HANDGUN ONLY. What you will be doing is weight train with you handgun as the weight and no you cant use something else as the weight unless you can hold it like you would your handgun. You will be doing wrist curls up and down, arm curls, full two hand and one hand arm extensions. With the extensions you want to hold them until almost muscle failure. Those holds will get longer and longer until you get to the point that you can hold that gun out there on target for as long as need be. Your finals will be to hold you stance for five minutes fire on target, then another, and another, three aimed held for five minutes shots in the kill zone at your chosen range.
BTY I do these drills three, four times a week and this is my very last option for field shooting I will use anythig as a rest before I resort to freehand shooting.