There are no restrictions on footwork in the rules. The umpire won't judge what footwork is best and what isn't. From a rulebook point of view, the slower the better, because if you're too fast, you could run afoul of §13.4.1 or §13.4.3 by touching the net or invading your opponent's court. If your only objective is not committing any fault, standing still is probably the safest. Umpires and other technical officials should walk at a normal pace unless instructed otherwise by the referee. There are no rules about this, but regulations: Therefore, for umpires and other technical officials, simple steps should be the way to go.
