How to swipe up into Mission Control and then swipe back down again without lifting fingers?
There is an app called Better Touch Tool. You can download it at their homepage. 

First, you hide preview if there is any, and then select Trackpad on the top screen. Before you start adding gestures, make sure to allow it to control computer in System Preferences > Accessibility



As you can see, I already set up the swipe up and down gestures. Below, you can select which gesture will it be (in this case, 3 finger swipe up and down). And under Predefined Action, you can search Mission control.