I mean, you've probably heard it here already, but the best thing to do is practice. Pick it up in the Battle Dojo. Ink the place up, now stand in one spot, aim at a target, shoot, aim at another one as quick and accurate as you can, shoot. Repeat until you find a comfortable sensitivity. Keep practicing this, then bring it to the Lobby to use on moving targets. Practice makes perfect, you may not do well at first, but with more practice, you'll get better and better, and if that's a weapon you truly enjoying using, use it, and you will do well, and have fun.
Also, I highly recommend using motion controls. There will be commonly occurring situations where you'll be sniping, possibly aiming down the sights and you'll have someone inking you up from behind. I'm telling you from experience, you will never be able to turn around quick enough without motion controls being active. With motion controls you can hit the analog stick in the direction you want to turn in, as well as, turn the gamepad and you'll turn extremely quick, and this will give you a fighting chance. You could even start charging your Charger while turn quickly to try to get off a quick OHKO.
Hope this helped, have fun!