How to Make Your Own Engineers Marking Out Blue

There are also many variations on the mixtures.... If your lapping precision surfaces together, a very small amount of shellac to lightly bind the pigment to the surface, quite thin with alcohol and a fair strength of dye.... so it rubs off, doesn't glue or bind the parts together, and it rubs off to show the high spots.... with fair contrast between the dyed area and the rubbed off area....

You sort of blend it to suit.

Scraping basics - Scraping flat - Part 1 and then Part 2.

https://www.mgtow.tv/v/2URB8p

https://www.mgtow.tv/v/V7dgfI