Here are some examples for Peteski's files.
I built this GHQ Dodge Caravan not too long after they first came out (about 30 years ago now!). Excuse the dust.
IIRC, I used Testors transparent candy red or maybe ruby red over bare pewter for the metallic look.
This is what I used for ink. It was used in compiter plotter pen. I got a bottle from work when they decommissioned the plotter 30+ years ago. Note that this is not a regular India Ink, but it is Latex based. It is slightly more viscous (but not much) and easier to work with. IIRC, I applied it with a wooden toothpick (I wish I have taken notes back then). I think I would just dip the toothpick in a puddle if ink, then touch it in the middle of the window opening and then spread it out to the edges of the window. The ink spread nicely without getting out of the window area.
Here is another example. This time I mixed a bit of white ink into the same black ink I used on the Caravan.
While these vehicles do not look bad, I still much prefer transparent windows.