Are these kits for contest puposes or for running on your railroad?
I sat beside one master modeller who was scratch building a plastic car and was drilling a line of holes, putting in the tiniest plastic rod, and cutting it off just above the surface.
I think Grandt line used to make castings ... or were those nut+bolt+washer?
Tradition was to run a clock gear along a thin strip of ?? and then glue that on. You can emboss the rivets on plastic and then carefully cut the head off and glue it on. (You were planning on spending 200 hours detailing this for the contest, no?)