Most right handed handgun shooters will shoot low and to their left under stress, and 90% of population is right handed. To counteract you should step hard to your left and continue moving in that direction to flank during a handgun fight. One of the dude's "oblique" movement in this video was to the right. Probability-wise, probably the best advice and course of action to take is move to left hard and fast asap. And provided you're adequately armed for quantity of assailants, moving backwards, including oblique is foolish -- move sideways or forward, but not back which has a high probability for falling and/or backing oneself into a corner/worse situation than moving forward where you can see best path for cover, concealment, footing, etc -- in the military, there's a reason withdraws are at least buddy drills.
Foot movement, find somewhere rocky (with lots of random fist size plus surface rocks) or uneven ground and practice moving quickly while not looking at your feet.
Football rope ladders and similar footwork drills teaching short but quick power steps are great footwork training as well... Actually any football drills geared towards linebackers are superb for any fighting, excluding groundwork -- which is basically wrestling.
