From the era you're talking about (pre NORAC) most of it was found in Rule 99:
99. When a train stops under circumstances in which it may be overtaken by another train, the flagman must go back immediately with flagman's signals a sufficient distance to insure full protection, placing two torpedoes, and when necessary, in addition, displaying lighted fusees.
When recalled, or relieved by another flagman, and safety to the train will permit, he may return.
When the conditions require, he will leave the torpedoes and a lighted fusee.
The front of the train must be protected in the same way when necessary by the forward trainman or fireman.
When a train is moving under circumstances in which it may be overtaken by another train, the flagman must take such action as may be necessary to insure full protection. By night, or by day when the view is obscured, lighted fusees must be thrown off at proper intervals.
Except in emergency, fusees and torpedoes will not be used by trainmen in automatic block signal system territory.
When day signals cannot be plainly seen, owing to weather or other conditions, night signals must also be used.
NOTE TO RULE 99. - When trains are operating under Automatic Block Signal System Rules, protection against following trains will have been complied with when full protection is afforded against trains moving on the same track at restricted speed.
99a. When a flagman is sent out with specific instructions affecting the authority of a train to proceed, such instructions must be in writing and must be shown the enginemen of all trains stopped by him.
99b. When a train crosses over to, or obstructs a track on which the current of traffic is in the opposite direction, it must, unless otherwise provided, first be protected as prescribed by Rule 99 in both directions on that track.
ALSO....
35. The following signals will be used by flagmen
Day signals
Night signals
A Red Flag, Torpedoes and Fusees.
A White Light, Torpedoes and Fusees.
35a. The following signals will be used by trainmen and firemen when protecting engine or front of train:
Day signals
Night signals
A Red Flag, Torpedoes and Fusees.
Torpedoes and Fusees.
Matthew (OV)