Re the South Line traffic.
As a boy in the 1960's my church held annual picnics in National Park, and my fathers army unit picnics were held on the same oval. So up the 128 steps to National Park station to set the train stopping disk. Then hide in the bushes. The Saturday procession of trains was constant. Many were block type trains but chalk markings like Melbourne, Mt Gambier, Karoonda, Loxton etc gave away the destinations a bit.
My father was a delivery driver and he regularly delivered to Mile End with electrical items, motors of various size , light fittings, rolls of wire etc.
The goods loading book was his bible.
All destinations were listed with closing days and times.
So if he had to get an item to Karoonda check the book and it had to be offloaded by say 2pm Monday to Friday. at say shed 1
LCL loadings would be dropped next to the M or DWF wagon chalked with Karoonda. There was forklift access at several points.
As the day progressed an extra wagon would be added if one was full or a four wheeler may be substituted if the M was needed for another run. Dad got to know the times when trains would be cut and shut or assembled to avoid delays or missing the drop off
As cut off time arrived the trains would be assembled , any extra wagons from Dry Creek and Port Adelaide would be marshalled in, and depart. So shed one would become a loading point for say Port Pirie.
A Saturday Picnic at National Park would see a progression of trains in both directions. Saturday would have been a day of extras to clear the yards and send out the wagons from Perth, Pirie etc. And also to send empties ready for the next week
Blocks of forty to fifty wagons in each direction. ( I could not tell if they were loaded or empty. Even OB and OBf were tarped in both directions to keep the inside clean and dry.
Demurrage was also a consideration as a VR wagon sitting empty at say Mile End would cost $ 8.00 per day. Friday was a good day to remove empties, especially before a long weekend.
A mixture of VR wagons, opens, M D etc would possibly be headed for Melbourne.
A mix of Of OB M FB, Dwf was probably bound for the mallee.
M etc, RX DW, DWf oil tanks was often bound for Mount Gambier.
Livestock was commonly in block trains headed for Murray Bridge, Naracoorte and Mount Gambier.
Keith was also a large livestock station
Chapmans at Nairne also had traffic to feed Chapmans, M vans, D vans and cattle and sheep vans.
With the empty pyrites wagons I understand that some loading for Nairne could be added as it seems that the loading of pyrites was normally about 8 wagons.
There were 25 pyrites wagons built. so 1 in shops, 8 on way to Nairne, 8 Being loaded at Nairne and 8 being unloaded at the Port would seem normal.
Trains to Strathalbyn , Cambrai, Sedan etc were required one or two times a week.
The Tailem Bend passenger often hauled excess Overland cars, products to and from Murray Bridge and early in container days containers.
Oil tanks were sent to almost every town that had a fuel agent or service station.
In the 60's the railways carried
Livestock, dairy products, LCL consignments, grain, fertilizers, oil, farm equipment, hay, departmental wagons, and in a perfectly made train there were coupler trailing loads to consider, but a train going to Say Pinnaroo would have the load for each station marshalled together if possible at Tailem Bend. At the rear of the train would be say an oil tank, an M , a C or S maybe an FB or OW, Next to that would be the next station with its assortment of wagons etc.
This could never be a perfect plan as trailing coupler loads applied to many classes of wagons, and empties had restrictions as well.
There was supposed to be a fender vehicle between petrol tanks and locos, A mixed train of livestock would see the guard trying to distance himself from the odour.
The Out of van or vans was usually next to the loco, as the guard may need assistance from the fireman or observer. And locomen did not like long walks. !!!
Add to this mix orders of empty wagons that were ordered. So O, OB, C Cf, S SF etc would be added in to this mix.
On the South line a 500 class steamer, 900 and 930 were capable of 500 tons each. An 830 was about 300 tons ( but had no dynamic braking)
Another thing to include is light engines attached, and shunt locos being changed over. They were usually attached to roadside goods because of speed restrictions.
Another thing to add confusion is loading going out of the normal order.
A load of a specific grain being taken from Say Keith to Strathalbyn for Lauckes.
It could be dropped at Balhannah and attached to the Victor Goods.
On the scavenger type trains you could see workmens vans being moved.
A neighbour of ours was a carpenter/ painter and had his own workshop and accommodation. He would often work on the Victor line. Start at Mt. Baker, then move to Bugle ranges, Strath, Finniss etc and his van would be moved by any convenient goods. When finished on a line he would head to the next destination.
So many trains, so many types of loading, so many combinations.
Another thing to consider to be prototypically accurate is weathering.
Trains do not stay clean and shiny very long.
7 to ten years was the supposed paint cycle
you would not see ten shiny m vans on a train. Maybe one or two clean ones, some in weathered dark grey from the 1950's, light grey post 1960's and into the AN era red, then green & gold and so on.
Even the Overland was like this. I remember a shot of the Overland at Mt Lofty. eight rooftops, six different variations of black, clean, dusty, brown.
Passenger cars were better overall, but not every carriage was repainted on the same day. The change from Green and cream to red took seven or eight years , then they changed class from 2nd to economy.
Also departmental loading, sleepers, ballast, rail, fuel, supplies in a D or DS van.
Enjoy choosing the different wagons.
If you find a copy of the working timetables from your chosen era you can gain a huge insight into loadings.