In message ,
" writes
Would they not at also at times release the brakes, using the rush of
air to let the guard know that the signal had cleared?

What about the platform repeaters, BTW?
If you got to a timing point a few minutes early then the bobby held you
until correct time. No one knowing they had a few minutes to wait
stood by the buttons ready to go so the driver normally give the train a
quick jolt. Releasing the E.P. Brakes might have done the trick if the
guard was observant, but a quick jolt was far more effective.
Repeaters are only any use where the platform is bent and the guard is
at his position, not reading a newspaper or book.
--
Clive