Have you searched the forum for information? Products like CerMark have been discussed here at length. There are some great tutorials on youtube as well about the application of CerMark and how it works.
And do realize you’ll only be leaving black/dark marks on the surface where the laser interacts with the coating, as the GF laser does not have the power and/or laser type to incise the metal like traditional techniques…
Yes i do…like screen printing on a coin. I understand that it doesnt actually break the surface of the metal. But i appreciate you asking if i realized that.
You wouldn’t need to spray the entire material, you could mask off the areas that won’t be marked in order to simplify cleanup a little.
Note that cermark will scratch and rub, i.e. if these coins are going on display, that’s fine, but if they are meant to be carried, the coating will wear over time.
As to settings, you’ll have to experiment with your material based on info from others who have used it and shared here. There’s not much but it’s no different to testing on wood or other materials. Be prepared for waste.