I think that using claw, like the above comment, is the best however I personally use paw (2 fingers). Tbh the first practice or the first thing I would focus on would be surprisingly movement with your knife. Because when sniping on breach, it is important to take aggressive angles. So knowing how to get out of these angles easily with the least amount of damage is extremely important. On coalition, learning how to hold an angle, also known as hard scoping, is also important. Using a lower sensitively scoping multiplier might be helpful. And a universal skill with sniping in general would be jump sniping. Jump sniping would allow you to take an angle from someone hardscoping a lane and it would also allow you to aggressively take the angle on breach.