I believe there are only 2 sidings at Chilcotts for bank engines, with both holding 4 engines, unless its changed.
Bank engine working refers to assisting trains from the rear, if on the front its referred to as assistant/assisting engines.
In days past banking was always performed on the rear of the train, steam days and when guards vans were on the train it was easy with the bankers just going onto the rear, when ready and they had the staff, whistle codes exchanged they pushed, just short of Ardglen Tunnel. The bank engine carried the section staff as far as Ardglen where a bank engine key was exchanged allowing the banker to return.
When diesels took over initially the banking did not change, the 48cl, then 47 and 49cl were fitted with a device on the cow catcher, that was swung up under the auto, on the lift bar there was a U channel welded on and the device would be swung up into the channel with a threaded pin screwed in to secure it in position. To swing it up you had to open the jaw of the auto and once in place test to see if the auto would remain open, if the auto shut, then you had to drop the device a extend it by screwing it out further (hard to explain it without a photo) once it was set, the same principle and working took place likewise with the staff.
With the longer wheat trains, a 44cl was stationed at Willow tree to assist in the front either to Pangella or MDI. A system later came into operation where 1800 tonne wheat trains started the next work program for bank and assisting of trains. The first train would depart WCK with 3x44cl and work to MDI, Stable the whole load and return to WCK LE, depending on the program, two of the 44's would be stabled at MDI. With the single 44 returning to WT, the 44's at MDI would be split and one left shut down on the train and the other in an empty road. Through evening the next wheat train that came through be a 1200 tonne train with a single 44cl and was assisted by the returned 44 to MDI, where it would pick up 1000 tones plus the on train 44 and form a full load to BUllock Island.
The assisting 44 would return to WT and perform the same duty with the next wheat train, and that would usually finish that working. In the meantime a 48 would come down LE to perform normal banking duties. There were other variations to that wheat train workings.
The next phase of working ended up being heavier trains and whilst still having the breakvans on, the so called bank engine working ended up becoming assistant engines full time. This was when approval was given for trains over 1800 tonnes to be assisted, which meant 2x44 ex WCK, and the assistant engines being a branch line engine and a main liner, but the rear engine of the bankers had to have heavy auto's, meaning it needed to be Mk4 48, 47, or 442, later changed to allow 45cl. What then took place was trains ex WCK could have any combo of 2 main liners to WT, if non heavy auto on the train, the bankers had to go on the train and the train engines on the front. It required reversing at WT and at MDI. As much as possible if a heavy draw gear loco was available ex WCK it was marshalled against the train meaning a straight attach and detach.
The removal of BV's and introduction of WB working again brought the engines on the rear, but as there was no lifting pins, and the heavier working, the banker had to couple up and have the air connected, the banking then went back all but to the old system. However this time round the banker was detached at a specific location on the southern side of the tunnel, where the train engines would pull up at set distance pegs and the banker would uncouple and the fireman ensured the air was tight. All communications at this time was two way radio. Initially the new working had 81cl on the roster but after mods were carried out initially on 2 of the 45cl they were brought into the working, following on from the first two another 2 were modified and allocated to WCK, and further tests allowing them to operate on trains to Ardglen and Tamworth, before the reclassing to 35cl
That was the working when I was medically retired end of 88.