But besides etchant and practice: What kind of mask was this? Do you happen to know temperature and concentration of the ferric chloride?
1 - printe the design on photo paper with a laser printer.
2 - clean the enclosure until it shines, and after that don't touch it with your fingers.
3 - iron the cr*ap out of it. You can see through the paper how the toner transfers to the enclosure.
4 - cover the big black areas with adhesive paper, this way you really gonna have a clean etching.
5 - etch it. I don't know the concentration, "use second hand" and watch the orange bubbles. The bubbles should be slow and lazy at the room temperature. Etch it for 2.5-3 minutes and then wash it, check the depth and the integrity of the toner. Etch it again for 2-3 minutes. It's not an exact formula and it depends on how large is the etching area.
Have fun and good luck! Don't "etch" your clothes/furniture/whatever, this way you avoid troubles with the wife/girlfriend.
