Use Sheriff only in DM. It may be frustrating at first, but it's really just like running with leg weights. Once you remove those weights, you run faster. Similarly, when you switch to vandal and you will aim better. Using the sheriff really helped me with tracking and trigger discipline. These skills transition really well to vandal or any gun for that matter.

I've been playing one or two games per day and I found that this method best helps me stay calibrated.

Some of you may already know this. If not, happy aiming :)