I'm curious about the printer, ink and paper you're using? Etching brass is a skill I'd like to learn.
I'm fairly new to the brass etching but my process is based on many few youtube videos about pcb board etching.
My printer is a cheap one from Amazon brother laser printer HL-L2300D around $50 with a starter cartridge.
Settings are below in a picture/ you want the print as dark and intense as possible.
many of the videos call for sanding and/or scotch bright preparation of the surface. It may work for a pcb board but for a finer detail polishing brass will give you a better results. With sanding there will be voids (from sanding) where ink will not stick and etching solution may go under the ink . Polishing will yield much better detail. So I sand my brass piece with 400 grit, then 600 then polish with green compound, then sand with 1200 grid and polish with rouge compound.
I then clean the brass with acetone like 5-8 times until there's on smudges or residue left.
once the brass is prepared I print my design onto a slick paper. I have used averey label paper ( the backing paper of a label) take off the actual label and trash it, print on the shiny side. Make sure not to touch anything with you fingers, cut the paper to size of the brass then carefully position paper on the brass.
Tape the paper to the brass carefully so it will not move. I was doing two plates at the same time so I sandwiched a piece of cardboard in between
If you are just doing one piece use a scrap, then you need to apply heat to transfer ink from paper to brass. You can use laminator, cloth iron etc. I did use an toaster oven set at 425 degrees for 15 minutes. After heat cycle, ink should have transferred to the brass and should look like this. Now you are ready for etching.
An hour and a half ferric chloride batch at 85-90 degrees should give you a very good result. This is what I did, it worked for me YMMV