How to paint letters cut in porous stone?

Quoted text begins.Are there less time-consuming methods to paint letters in porous stone?
And what kind of paint do you use?
And do I need to use a kind of primer (it is for outdoor-use).
End of quote.

Michiel,

You could try using a single coat of acrylic natural-look sealer (applied with a
sponge) all over the stone before painting the letters. The sealer makes the
stone less porous, so it makes the paint flow easier into the lettering and
helps with cleaning up any smudges outside the letters, effectively acting as a
primer for the paint.

You can use any sort of paint, acrylic or oil. Oil-based lasts longer.

Simon