The ones in the bag are unused.
The three laid out are used, and mirror shiny.
There's little difference in the smoothness of new ones and shiny used. It's like a coating has been rubbed off the used ones
My question is if machining and grinding your own, how practical/realistic is it to...
You would need to assemble the head. Measure and order shims to suit.
If you were starting completely fresh, have a selection of shims of different sizes so you have a baseline to measure clearances with, and calculate from there.
Then order what you need.
How would you describe the finished surface then?
The three not in a bag are so shiny its hard to photograph them. Look closely, you can see my finger prints on the shiny surface.
They are extremely flat. Seem to be coated or anodised?
I have new/unused OEM shims that look the same as...
This is simple version. Hooks under cam, rests on rims of shim bucket, rotate tool to comress spring and hold bucket down, use magnet to pluck shim out. Release spring while you measure shim. Repeat to replace shim.
Or this. More fiddly, and slower IMO.
The centre tongue hooks under cam...
You don't need to remove cams. There's a simple tool that cab be bought or made to compress springs/buckets or at a time. Use a magnet and small screw driver to remove shim. Measure, replace shim for later.
When I've done shims, I measured clearances, measured existing shims. Then using the spread sheet/Chart in the FSM, work out what shims i needed to order.
It means pulling rocker cover and throttle body off to measure, and again to change the shims.