I am trying to make an old steel framing square more usable. I've checked it for squareness and need to adjust it just a hair which I will do with a center punch.

My question, though, is how to fill the etched numbers, lines, etc. so they are readable. Many moons ago, I used to have a tube-style paint stick which you could rub on etched areas then rub off the extra. This worked great but I can't seem to find something like that now. Anyone have any idea what it might be called or even if it is still available? Rubbing paint on works, but the stick was much less messy because it was almost like a wax.

Any help would be most welcome.