Coming in late on this question. However hope the following is of help.
Many of the open TT's had originally been cut out with a bed of sand & bricks set in the sloped area of the pit. The centre pinions were built on concrete footings as was the rail, & mini cut sleepers. Over time the bricks would move, break up & become a danger, & in some cases were removed, or nature took over with dirt blowing in, meaning they were covered in weeds & other growth. The bridge proved to be a good mower in those cases.
The wheels on the outside, were not really part of the turning process, as these TT's & all the manual types on the NSWGR were balancing types, that meant for any engine to be turned the loco had to be set correctly & in balance on the table bridge. When balanced properly the wheels on both end were sitting in the air, same as during the turning process, although when the balance was precise the bridge could wobble up & down with the wheels occasionally touching the rails. If the wheels touched too much the bridge would or could stop turning.
The primary purpose for the wheels was that when the engine ran & off the bridge, the whole bridge would drop on that end, the wheel was set so that the bridge rail was set just below the entry/exit road rail top. When bringing the engine on to the bridge the fireman had to stand on the bridge at the entry end, which would allow the bridge to drop down, with the wheels taking the wait, at that point the fireman got off the bridge & waved the drive onto the bridge, once the whole Engine & Tender were on, caution signals were given so that a quick stop would be made when balanced.
It was rare to get the balance with the first move, as the bridge balance was passed it would drop hard on the other side, again the other end wheels took the brunt. This allowed the driver to then wind the hand brake on partially, & very slowly move back to get the balance, when that was obtained, he stopped very quick, & if the bridge rocked up & down things were right. The hand brake was fully applied & cylinder cocks opened, to stop any movement. The driver would help the fireman start the TT moving, when balanced properly it was very easy & you only had to get the bridge started, & it roll all the way round, push to far & it would keep going.
Once moving you walked alongside until you got to the exit road, where you lifted the paul & got read to drop it on the concrete edging to the paul cut out locking recess. As the engine moved off again the fireman stood on the departure end to drop the bridge off balance.
Roachie mentioned the 36c & problems, that happened very much at Armidale, until a new DLE came there & he told the shed crews to not water the engine prior to turning, this had been something also learned with the 59cl, these "big engines" (for these depots) such as the pigs & 59cl needed to have a maximum of half a tender full of water to be able to gain the appropriate balance to turn them without splitting. The TT at Richmond was a problem for the 59cl unless there was less than half a tender full of water
When you consider that most of the small depots in the country including Picton, there was few staff attached to the depots for general cleaning duties, the Trainee enginemen, or cleaners as they started off prior to being qualified for firing duties, had to contend with cab cleaning as well as calling crews, taking out call papers & other duties, the shed crew, were there to sit pilot for assisting the mails or similar, coal & rake out the engines. Usually most had a fitter & mate for the mechanical work & a single labourer on day shift to clean around the depot & assist the fitters as required.