You won't find it. Why would anyone publish instructions or guides for "temporary excavations"? That's generally the time for a cave in, when first being dug.
A few state DOT's in the Northeast generally allow a 25% reduction to the factor of safety for temporary conditions, but it depends on what you are doing. Is this for a sheeting design, open trench, etc.?
If this is a temporary excavation, I suggest to use/rent a metal trench box instead of sheeting. Local shoring company maybe able to come up something for you.
For global slope stability, a minimum FS of 1.2 may be adopted if there is no sensitive structure/utility nearby. If there is, ground movement/impact on adjacent structure/utility is likely the governing factors, FS may be 1.5 or higher.