You don’t need to be shooting to find the best backstrap and grip. Start at home with dry presentations and firing. If you can’t consistently get on target comfortably at home, you shouldn’t be able to do any better at the range. Your trial and error adjustment can be done at home basically for free rather than at the range for $.25 per mistake.
Unload and remove ammo from the room. Keep an empty mag in the gun. Put a small target on a wall ~20’ away. Do these presentations one handed. It is too easy to artificially force a gun into alignment using your second hand. This is not a competition to see how great you are at getting on target. It is an exercise to determine whether you need a different backstrap to point naturally.
Ideally, do these exercises drawing from a holster. If not, then from your waistband, or even a table or chair. Do not start with the gun in your hand. You need to establish your best grip on the gun that will be repeatable and controllable. Grip the gun as high as possible. Grip it tightly, but not so much as to cause the gun to shake. I like to put my trigger finger high above the trigger pointing straight toward the target until I actually do my dry firing.
Present the gun at least 10 times after each change you make. Note carefully where it is naturally pointing in reference to the target. Don’t force it onto the target.
If you are close to aligned on the target, especially if you are just a little left or right, adjust your grip on the gun. If you are way off, especially above or below the target, you probably would benefit from a different backstrap. The goal is to find the backstrap that will give you the consistently closest presentation to good sight alignment on the target with the least amount of grip adjustment necessary.
Still going one handed with your best backstrap and grip, start dry firing and see how little you make the gun jump when you press the trigger straight rearward without touching the frame. Adjust your finger on the trigger for the least movement of the sights. If you feel you are forcing the gun on target or cannot keep it held directly at the target, you need more dry fire practice before wasting rounds at the range.
When you feel pretty good with your presentations and pointing, add your second hand for stability, not for aiming. Your trigger hand needs to be the aiming one. If your second hand is pushing the gun to the aiming point, then it is fighting your trigger hand. This is not natural pointing, but muscling the gun. It is one of the leading causes of inconsistent accuracy.
While shooting at the range is gobs of fun even when you are not very accurate, it is much more rewarding when you can actually hit precisely where you are aiming. The fundamentals of grip, sight alignment and trigger pull cannot be ignored. They all can be practiced at home without $$ cost.