Re inking or painting sight knobs

How do you go about re inking the numbers on a Garand (or any other sight/item)? Especially the tiny areas.

Did they use ink? (this is what silk screen uses). I would think they simply wiped the ink across to fill in using a mask or template to hide off the areas to not be filled but what technique is used and does anyone know of a "you tube" or some site that has pictures and instructions? Was there a specific color? I note the good marked ones show a beige but were they white when original? Lot of different whites!

I have very easily filled in a Winchester "Red Letter" Model 37 shotgun but the tiny numbers will be a challenge without a good technique and some training.

What is the correct term?

Any help appreciated.

Te item used is like a grease pencil. Stroked on then wiped off. Your machine supply shops should understand what you want...