I understand you wanting to use the shapeways system but I have had several pieces from them finished in there so called frosted ultra detail, I have found all the pieces to have a slight texture to their finish and at times obscuring smaller detail.
Even in the picture you posted (sprayed black ) you can see the issues apparent compare that to the earlier crisp clean sculpt you had done, I honestly would recommend casting that one up in resin it may be more hassle but you would get a better finish and more customers.
I honestly can say I would not buy another Shapeway print sorry but thats the truth, I also like the cleaner cloak however I still liked the skull encrusted one you did myself you have a good talent