All of the above should be fine.
Sharpie is absolutely the worst, and is not even good for glass edge blackening, I've had it break down and fail (reasons unknown) on several tries. And it is extremely shiny at low angles.
The Black 3.0 requires explanation, it seems there is a branch of art where ultra flat blacks play a role. Vanta (?) requires special procedures, and Stuart Semple Black 3.0 has cost, apllication or availability issues IIRC. Apparently there is some big flatness war, not that I cared.
But Stuart Semple Black 2.0 is amazingly flat and easily bought on Amazon.
In my casual testing it beat everything I had or tried, particularly at low angles. It beat the nice Vixen black in their big high end refractor focuser, which has excellent blackening.
It is easy to apply, but is easiest for smallish areas like yours.
For glass edges I use Higgins Black Magic India Ink 'markers'
in marker or marker-brush form.
Excellent and durable in lens / prism edge blackening.
I've never tried it on metal. It is labeled semi matte, but is very black on glass and really kills reflections. It is said to be waterproof but high purity ethanol can take it off.