I created a post about how I “etched” brass a while back. You can see that post here.
The settings for this action are:
Power: 100
Speed: 100
LPI: 225
1 Pass
I used a total of 3 light coats of Dry Moly Lube on some brass that I had cleaned and polished with 0000 steel wool.
No idea how I missed the original post! Sure glad you posted your settings to trigger viewing the original!
Bookmarked! Thanks so much.
Ha ha. I probably wound not have but someone commented asking for the settings. I meant to go back and do this, but just never did. Life’s too busy right now. 
Thanks for the info. Was just amazed at the time to actually engrave things. Had to split my 4x8 item into 9 chunks at almost 3hrs each.