The slugs we used at West Colton way back when, were primarily extra braking, on cuts without air. The Colton hump yard started doing double cuts (superlong cuts) by coupling up two cuts of whole inbound trains (remember they put in a mid yard ladder in the receiving yard) to be able to supposedly yard two trains at a time. West Colton was a sucky hump job to work, with or without slug sets, though.

West Colton's receiving yard was on a slight down hill grade, toward the "hump". That grade actually got slightly worse the closer you got the hump, down along the engine lead, and main tower, and the "hump" was just enough of a rise to theoretically get the pin. But, unlike the LA hump, where you were on a pretty steep grade at the Top of A yard, and pretty much be in a bowl balanced and pushing "up" the hump, at West Colton you were going "down" to the "hump" and the slack was always running in and out, because your speed was always creeping up on you, so you would have to use that slug with the independent brakes to "slow down", and they would miss pins there all of the time, because the cut became stretched.

So my memories of slugs are not as fond or dear due to my experience using them long ago, on a distant planet, in another galaxy, far, far, away. An interesting concept and because they were MU'd I do seem to recall that we got extra pay for the added weight on drivers (IIRC? or have I completely lost it?).