Thank you for your post. It's my understanding that earlier brake stand types e.g. #6L had smaller reduction increments. Early locomotives (including diesels) saw a minimum application of 5 lbs. drop in train line pressure. I specifically use the term 'drop' since most readers probably don't know that a real train looses pressure in the train line to gain pressure in each car's brake cylinder.
It's also my understanding that since the 26L brake stand was made universal in North American railroading, a minimum service application is now a 6 lb drop and full service application means a 26 lb. drop.
The retired engineer I've been in contact with sent a reply to your question. He wrote, "It's called Power Braking. Whatever throttle position I need to stretch the train. The purpose for this is to get your train stretched tight so you don't bust a knuckle of yank an entire draw bar out of a car, from having slack in the train. As for what throttle position I have the throttle in, is whatever throttle position I need in order to make sure I get it stretched and apply the train brake and throttle back as your train slows to a stop or approaches the speed I want to be at. Unless you are going for Dynamic braking, then of course you want the throttle in the idle position. ... There are a lot of things that comes into play here, not just one scenario. I was considered one of the better Engineers for my method of handling a train. Smooth starts, smooth stops. Two knuckles to my credit that was caused by the train going into emergency due to a broken train line or air hose. Not bad for a career time frame. I took Pride in my train handling, but I had good teachers. When we had Cabooses the men on it didn't have to brace themselves for a run in or run out and the possibility of getting thrown from one end of the Caboose to the other, which did happen many times, injuring one or both men and also dislodging the stove, desk or anything else bolted to the floor. A slack run in from 50 or 60 mph is like running into a brick wall. Also, we were not referred to as "drivers", as in order to "drive" you have to have a steering wheel, which you don't have in a locomotive. We were referred to as "Engineers". We ran the train, we didn't drive it.
I won't get into a fray with him, but ask that "driver" what he
does when his train is in a drift mode. As it will get slack in
it, depending on the terrain that he is running in. You either
power brake or dynamic brake, depending on what you anticipate you
have to do ahead of you. If you set the train brake in a drift
mode, I guarantee you will tear your train apart unless you come
to a full stop. I'm certain he will say Dynamic You have to choose
the best method for what ever occurs, when it occurs. Train brakes
do not all release at once or at the same time. They all release
differently. I learned to Power Brake first, because not all
engines had working Dynamic Brakes, until later on.
Dynamic braking takes time, to transition from throttled running
to that mode. If your in throttled running it's quicker to Power
Brake as opposed to Dynamic. Going down grade, Dynamic is the
ticket. But there was a time when we had only the air brake to
assist in keeping your train under control.
I learned a valuable lesson from and Old Head Engineer, that said. You will only make a good Engineer, when you can "Feel" your train from the seat of your pants. And that is how I did it. He was a good Teacher.
End of story,"
I guess, similar to N. American engineers, e.g. Electronic engineers, software engineers, mechanical engineers and locomotive engineers, etc., there are several different versions of drivers in the commonwealth. In Canada we use locomotive engineer or just engineer. I became aware of the term, locomotive driver, when my children were young - watching the British version (Ringo Starr was the narrator) of Thomas the Tank engine. :-)