LIPSTICK. A use for lipstick for mating surfaces.

[Toolmaker51]

Colorful grease; no kidding. I don't care what is being matched, there are ridiculous shades that will contrast.
Felt tip is great, up to point it soaks into wood.
Another material that can transfer markings, is carbon paper (ie typists). Biggest advantages; not only very thin, but can lay very flat.
First time was inletting a 91 Argentine Mauser to a stock blank with only a rough barrel channel. With receiver home, paper monitored progress in the tightest bolt handle cutout "ever".