well anyway, here's the best screenshot I can get, this is the core of my most recent openttd network, though I started a mainline along the coast off to the top left which is pretty extensive at this point
this was the first industry I focused on, and remains my biggest station complex. Furnace is the drop-off for raw materials (iron ore, coal, scrap metal), Gefingway Woods is the pickup for steel: one set of platforms feed back into the previous screenshot downward, the others directly to the aforementioned new mainline. Sutfield Woods is a separate drop-off for a couple of nearby raw material industries
this is the largest junction in my network. you can see two sets of doubled lines going bottom-right to top-left (just about in the latter case, there's branch lines quite close to the junction!). those lines came later: the big station is off to the top-right and started being supplied from the bottom-left, you can just about see single lines in each direction there, but the top-right has a station right in the middle which muddles things substantially
the steel sent to the newer mainline goes to the processing plant at the top right which produces goods which come back down to the port (as well as having other things delivered to it), which produces engineering goods (amongst other things). those engineering goods are loaded onto ships which go to... the next screenshot
Sutfield Docks in the top left has engineering goods transferred to it. trams take them to the coal mine and scrap metal yard, improving their production. those are the industries which supply that side station from the earlier screenshot! you can also see a train which takes them to a couple of further industries.
here ends the dry dick openttd posting, thank you @drybonesofficial for activating my trap card
so to summarise, the steel is turned into goods which are turned into engineering supplies which improve the output of iron ore, coal and scrap metal which are turned into steel which is turned into goods which are turned into engineering supplies which improve the output of iron ore, coal and scrap metal which are turned into steel which is turned into goods which are turned into engineering supplies which improve the output of iron ore, coal and scrap metal which are turned into steel which is