I haven’t done brass yet, but I have done a ton of Aluminum. Rather than try to do it all on the Glowforge, I use the laser to remove an acid resist from the material, I then use an acid (Ferric Chloride works on brass I believe.) to etch the areas where the resist was removed by the laser. With experimentation, you can get very good results with the laser.
You can get better results if you use a photosensitive resist, and a film positive (like a transparency only more opaque and higher resolution.) This process also requires a UV light source to do the exposure. It’s not an expensive process, but you can’t get photo positives done at staples. I used to get them from a local printer, but it’s almost all digital to plate nowadays. I got some done here. https://www.anthemprintingsf.com/Film-Output-Services-s/232.htm