There was always talk of PN wanting to blank off the release position on the B7's fitted to their 48's, but in my time with them, it wasn't done on any loco's I worked - even though we were instructed not to use it for fear of overcharging the BP.
KV, sticking brakes with the older BV's was more often caused with vehicles that had old triple valves, and grade control valves that tended to get clogged up with road grime including brake dust, especially when older trains had to operate in HP position for long heavy grade descents. Even further back was the requirement to set hand brakes as well, again creating the continual brake dust problem. Later Relay and choke valve equipped wagons did not seem to have the same problem, 26L and later BV's were better with those types of wagons as they did not have the kick ability.
We were told to have the rotary valve setting for goods services at 70psi 60 for Passenger stock. Descending the blue mountains, and Illawarra Mountain you put the BP up to 90psi, as you came to the bottom of the grades, you began reducing the rotary valve back to the normal setting of 70, at the last such reduction you gave it a very heavy reduction once you came to a stand, and then released the brakes. Off the escarpment you generally didn't worry if you were only going into Unanderra sidings, but if heading to PTK you would.
Off the mountains, the fireman and guard met half way at either Springwood or Valley, putting the GCV's back to IP or exh depending on the driver, barring in mind that with regen on the 46 would control the trains exceptionally well for the rest of the journey, also on the short north to and from Gosford on the 1:40's so no need of the GCV's except in IP.
When I worked with drivers in steam days, and prior to going into the A/Driver school, the big thing in the teaching and use of the old BV's was that when you released the brakes, you held the handle over in the full release position for 1 second for every vehicle on the train, be that #4, A6ET, 6ET, A7EL, B7El and 7EL, bring the handle back to Release and Running (R&R) for 2 seconds and give a 1 second kick to full release back to R&R.
The idea, and it mostly worked was that you sent an extra amount of air through the Brake pipe, above the rotaryvalve/auxillaries setting in basically a rushed setting to push any dirt out of the triples etc, likewise the secondary short kick. That would normally work without a lot of problems, except as I said with some old vehicles fitted with Triples, and or GCV's which were put into positions other than Exhaust (normal release), most sticking brakes occured with the triples in IP, retarded release, owing to the dirt build up. If the sticking continued we cut them out out tied a defect card on the Triple valve handle.
Over the years I had relatively few sticking brake encounters, as what I found was that in the main, most trains did not need the GCV's set in other than IP, in fact many drivers even when working high wheelers would ask the examiners to not put them in, or at crew change points if the train had an examiner check at the changeover point, would ask for them to be taken out. That was especially the case on the Short North and Short South, never had them in out of WCK except heading to BMD, or down the Moonbis, and Illawarra, except the mountain and heavy trains to Enfield with 48cl working them.
In my later years, I noticed some new men, not using the old methods, and simply putting the handles into R&R on all old equipped loco's.
In response to what Gordon had to say, many shunters when a train came in and had to be shunted, would walk the train and tie a minimum number of hand brakes on in order to hold the train, and walk back and place a piece of small ballast/stick or whatever was found on the ground into the release handles throat, in order to hold the release port open without them standing and holding it open. Problems occured though, if the fitted piece broke and some was stuck in the ports throat, which could cause faulty brakes on that vehicle, unless it was blown out when the train was made up and the air went through the train.
I watch many of the modern trains go through Wyong, and I find that there are as many vehicles with flat wheels these days if not more than in my times, that's even on EOT pulse (or whatever its called) braking, another topic I guess, but often related to the operation of the air.
PS, as an edit in. The old #4 BV, used on most steam loco's including the 57cl and 36cl but with an engine only brake plus #4 for train working, the regulations provided for the handle to be place in the full release position when descending the two main mountains. The compressors had a governor that was set to a constant 100psi for the main reservoir, with this method you operated at the full MR air charge going down the 30's and when at the bottom you put the handle back to R&R at the rotary valve setting. This meant that in the standing they had to make 3 very heavy reductions and the normal release operations to get the brakes release without the danger of sticking brakes. Also, in the steam days, with those loco's (not the 58's or engines fitted with A6ET BV's) part of the fireman and guards job was as they released the hand brakes they also had to drain any air by holding the release valve open.