Craig: On those tie plates, I might try hand-milling (filing) them out of some smaller stock rail. Come to think of it I have some plastic track - NewBrite or something like that - around here somewhere, and that might be easier to file to shape.
I don’t think you told us what you are studying. If it were only jewellery-making you’d have a lot of your parts made in the shade.
You might go to a local jeweller anyway and have some of these parts cast in brass or bronze. Come to think of it, he might be able to offer you good advice on a lot of the challenging parts you’ve been talking about here.
Might be worthwhile for you to take a job with a jeweller, pick up all kinds of tips, learn about tools and suppliers, etc.
You can also take extension courses in jewellery making, but you’d have to make sure in advance that it covered the topics that would profit a model builder.
The reason I mention all this is because I once knew a guy who was a jeweller hobbyist. Among his posessions was one he particularly prided himself on - a miniature forge.
Unfortunately, I moved away before I had a chance to cultivate his friendship or learn much more, but the memory has stayed with me over 20 years later. I’ve always been curious where those skills might have led, modelling-wise.
I suspect that some of the old producers of brass detail parts used jeweller’s skills, techniques, tools and materials.
Just some food for thought.