Dry fire at home and practice on:
- a smooth but rapid drawing with minimal extra movement
- rapid acquisition of the front sight after the draw
- smooth and quick transitions between targets
At the range, learn the rhythm of your gun during rapid fire (if possible). Also practice to reset your trigger quickly without letting it all the way out. A smooth trigger press during rapid shooting is critical, so you want to avoid beating on it and causing your gun to move more than necessary. Getting your body to learn and use the reset point of your trigger (rather than the full take-up) helps with this.
You don't have to shoot it like a laser-aimed machine gun, but you do need to try to recognize and eliminate inefficiencies in your movement, focus on that front sight, and press the trigger smoothly. Do this, and it is pretty easy to jump from Marksman to Sharpshooter.
do a google search for " IDPA classifier tips"