Honestly, I wouldn’t follow my example here. The more I look at it, the less happy i am with my settings. I think I burned it a hair too hard, the shadows lost more detail than I wanted. I’m redoing it right now at same power but higher speed and at a larger size (17" wide by about 8" tall, or 43x20cm – it’s going to take 2 hours!).
My material choice isn’t ideal either, using baltic birch ply. Plywood is sketchy for engraves because if you go too deep you hit glue+internal layers, which changes the look of the darks. While I’m sure that this can be used for good, right now it’s firmly evil.
When I get serious about a final version of this, I’ll probably find a nice blank of maple or basswood to do it on. I’d say to use proofgrade stuff, but it’s masked, and I’d want to get a good look at the surface before trying it, a knot will impact the final piece in a big way.
Besides, I curved this piece so that there is no true white anywhere, I find that the transition from “barely engraved” to “not engraved” is too harsh, so I put my lightest whites at something just under 255. This means that the advantage of proofgrade being prefinished is negated, because I’m ablating the whole thing. (hint to GF, sell unfinished and or unmasked proofgrade at a discount!).
So, in the end, about the settings: nah 
You don’t want any of this nonsense.
EDIT: I think it already looks much better, engraving dust and all:
