J-flicking: flicking your mouse with high DPI immediately after initiating a swing, allowing you to pull a 180 turn (or more, if you want). There are two main mechanics you can do with this. You can either just play like that all the time, or you can use a DPI clutch to swap between low and high sensitivity (common feature on most gaming mice). This is typically accomplished by playing at extremely high sensitivity. If you turn enough between checks (within a single frame) to turn more than the 90 degree limit, you will be allowed to do so and just be locked out of. The way Blight's turn restriction works is that the game checks your Momentum vector and your Look vector once per frame, and if the angle difference is more than 90 when it checks, you won't be allowed to turn any further. This allows you to turn up to an additional 90 degrees.
When you initiate a rush attack, your momentum vector snaps to your look vector. Your look and momentum vectors can ordinarily differ by a maximum of 90 degrees (again, this can be changed). Your look vector governs the starting angle for any rush attacks you attempt to make. Slipping is initially frustrating, but can be taken advantage of once you know where you're going to end up sliding. Survivors are slippery (as they are not terrain) Newer shack variants, such as Macmillan and Coldwind, are slippery (except the corners). What objects are slippery basically has to be memorized, but in general you can think of it as "if attempting to attack that terrain with your weapon held at head level would result in your weapon colliding rather than whiffing, you can bump." If your momentum vector collides with terrain with an angle steeper than 45 degrees, and it is a valid "non-slippery" object, you will bump. Your Momentum vector governs your bumping.
Your "Momentum" vector generally starts off equal to your "Look" vector (though we can change this), and your momentum will adjust to match any changes to your look vector. While you rush, there are two vectors that matter.