Graver: What i would do, measure the mm width of each strand of your weave, then go to a jewelry supply place like www.riogrande.com and get 3 things, a round needle file, a graver handle, and a Graver blank. Then make a "U" shape that is as close to the profile of each strand of your design, then holding the Graver about 20-30 degrees from the pendent (it should be almost parallel with the pendent) LIGHTLY push forward, scraping everything smooth... Mind you, the more smooth and polished the Graver is, the more smooth and polished the metal will be after you cut it. You can see some examples of this type of cutting action if you search for videos on Hand Engraving, or Diamond Setting. Just remember to secure your piece so you don't accidentally cut your self. Gravers are usually sharp, and will slip... even when you are skilled.
Soda: Coke works GREAT as a basic acid after casting, and doing minor surface cleaning, but will do nothing for the actual topography of the surface, and it WILL bring out more of the bronze in the Stainless alloy that Shapeways uses.
Pictures: Agreed! Pictures will be Awesome!
Wire Brush: either by hand or a rotary wire brush would look awesome. it gives a nice mat shine to the stainless, not too bright, not too dull... but it wont remove the printing artifacts.. for that you will have to use intricate hand methods.
Honestly, it all depends on how you want your design to look. I have seen pieces with varying degrees of polish, and they all look Awesome! And hey, if you mess up, then just order another. Sometimes mistakes are the best part of learning.
Ray