I'm dyeing and then clear coating my parts with 2 component automotive paint with a spray gun. First it has to be tumbled for 6 hours (I think shapeways does 2 hours?), otherwise the coating will turn out like sandpaper. I use a different 3D printing company that has a little box to tick for "keep this orientation", and I can put my model in at 45 degrees to reduce print lines. They also give you an account manager, and I can ask her to polish my parts for 6 hours.
However, the company just increased prices by 20% so I'm searching again for another company.
The print orientation and tumbling times are really important for the coating process. The surface has to be extremely smooth. But the spray painting is probably the most labor intensive aspect of my production and I'm wondering if there is some automated way to coat these parts. I don't think it's economical for me to buy a FANUC robot.
http://www.fanuc.co.jp/en/product/catalog/pdf/robot/Robot%20 i%20series%28E%29_v24.pdf
Building a robot would be quite an adventure.
So I'm thinking about these electroplating, electrostatic coatings,either dipped or sprayed. I just met a guy who makes camera equipment using SLA and he has a company electroplating his parts, and they can do his printing and dipping on the same day. But I don't know about PA12.
Also, electroplating with metal pigments greatly reduces the WSF flexibility, but I would still like to keep the 20-24% flex vs the 4-5% of ABS.