Yeah the are good and have a 100% hit rate in pvp?
BasicLly it is a bit of pratice, you shoot the monster and shoot again just as your damage number dissappears. I am out of practise in this since I seldom use my gunnerfox. Maybe someone can make a video?
And once you have mastered timed crits; it is possible to fit in a skill in between them. I have seen this done but have never done it myself.
Also then can do about the same damage as powershot
Edit: try prastising on rocks and trees.