gmpullmanI read some first-hand interviews with engine crews on the Pennsy's T1s and they learned a trick to help them get out of the station with less chance of slipping was to sand a couple hundred feet while backing down to the train before tying on.
Where this was a concern, having enough sand to get out of starting torque peakiness with poppet valves when driven a la K4 (yank the throttle open ASAP and control with the reverse) might be essential. Whether or not enough of the 'ground in' sand from the laydown would remain on the contact patch upon restarting is not well recorded...
This technique might have been of use for a couple other classes of duplex with two-axle leading engines, and perhaps for light four-coupleds like the Milwaukee As, the Jubilees, or Lady Baltimore. It might also have been advantageous to lay sand strategically in areas where the engine would be encountering increased train resistance, e.g, going through multiple slips or crossovers in approach track layout. Some of the extreme low-speed slipping recorded for T1s appears to be resulting from this kind of effect.
I have not gotten far along enough in simulation to tell you the likely actuation lag on PRR forward-engine sanders -- did not think it would be that long, and of course could be commanded more than a few seconds before starting, and effective release from the pipes confirmed from someone in the ground (a thing that would be much easier with modern radio!)