make your sensitivity high enough that you can do a 360
then, if it's not low enough or not high enough, lower/raise it until you can comfortably flick rocketjump
then, if it's not low enough, lower it until you can comfortably aim vertically at mid/long range feet
then, if it's too low, raise it until you can comfortably do a flick 180 from any reasonable point on your mousepad
you can reorder the steps in order of least to most important to you but the most important part is that some useless guy on the internet is giving you advice on how to get a comfortable and useful sensitivity. right?
vilewhatever you're comfortable with.